DC motor and controlling system therefor

ABSTRACT

A dc motor wherein a driving force thereof can be used effectively with a simple and compact mechanical construction and a motor controlling system which can control such a dc motor to be driven efficiently. The motor comprises at least two coils, and change-over means for changing electric connection of the coils to change over the motor, when power is selectively supplied to the coils, between a first mode in which the torque produced is relatively high and the rotational frequency is relatively low and a second mode in which the torque is relatively low and the rotational frequency is relatively high. The motor controlling system includes selecting means for automatically selecting one of the first and second modes to control the change-over means is response to a given condition of the motor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a dc motor which is well suitably used to windand rewind a film in a camera or a like apparatus and a controllingsystem for a dc motor.

2. Description of the Prior Art

Various dc motors which are driven by a voltage supplied thereto from apower source battery are already known. However, in such dc motors,reduction in voltage of the power source battery may sometimes result indelay of operation or halting of a mechanism which is connected to bedriven by the dc motor.

Therefore, an improved arrangement has been proposed, for example, by aJapanese patent laid-open No. 60-194433, wherein a transmissionmechanism for transmitting rotation of a motor to a driven mechanismincludes, in order to use the driving force of the motor as effectivelyas possible, two gear trains whereby if the rotational speed of themotor decreases, the motor is temporarily rotated in the reversedirection to change over from the normal high torque gear train to theother lower torque gear train so that the driven mechanism may be drivenat a low speed.

However, such conventional arrangements of the type mentioned requirestwo different gear trains as a transmission mechanism as well as achange-over mechanism for selectively using one of the two gear trainsin order that a motor may be driven also at a low speed. Accordingly, itis a drawback of the conventional arrangements that they are complicatedin mechanical construction and hence they may have a large overall sizeand be produced at a high production cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a dc motor wherein adriving force thereof can be used effectively with a simplified andcompact mechanical construction.

It is another object of the invention to provide a motor controllingsystem which can control the dc motor of the type mentioned to be drivenefficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating a concept of the presentinvention;

FIG. 2 is a graph illustrating a relationship of torque produced by amotor to a rotational frequency and electric current flow of the motor;

FIG. 3 is a fragmentary perspective view of a dc motor showing a firstembodiment of the present invention;

FIG. 4 is a bottom plan view of an upper cover of the motor of FIG. 3;

FIG. 5 is a transverse sectional view of the motor of FIG. 3;

FIG. 6 is a longitudinal sectional view of the motor of FIG. 3;

FIG. 7 is a general perspective view of the motor of FIG. 3;

FIG. 8 is a diagrammatic representation illustrating electric connectionof the motor of FIG. 3;

FIG. 9 is a longitudinal sectional view of a dc motor showing a secondembodiment of the invention;

FIG. 10 is a transverse sectional view of the motor of FIG. 9;

FIG. 11 is a longitudinal sectional view of a dc motor showing a thirdembodiment of the invention;

FIG. 12 is a transverse sectional view taken along line XII--XII andXII'--XII' of FIG. 11;

FIG. 13 is a longitudinal sectional view of a dc motor showing a fourthembodiment of the invention;

FIG. 14 is a transverse sectional view taken along line XIV-XIV of FIG.13;

FIG. 15 is a diagrammatic representation illustrating electricconnection of the motor of FIG. 13;

FIG. 16 is a longitudinal sectional view of a dc motor of a fifthembodiment of the invention;

FIG. 17 is a transverse sectional view taken along line XVII--XVII ofFIGS. 16;

FIG. 18 is a longitudinal sectional view of a dc motor showing a sixthembodiment of the invention;

FIG. 19 is a partial longitudinal sectional view of a dc motor showing aseventh embodiment of the invention;

FIG. 20 is a transverse sectional view of the motor of FIG. 19;

FIG. 21 is a perspective view of a film winding and rewinding mechanismof a camera showing a first embodiment of motor controlling system ofthe present invention;

FIG. 22 is a perspective view showing a shutter charging mechanism ofthe camera of FIG. 21;

FIG. 23 is a block diagram showing an electric circuit of the motorcontrolling system of FIG. 21;

FIG. 24 is a flow chart illustrating general operation of the circuit ofFIG. 23;

FIG. 25 is a flow chart illustrating an exposure information readingsubroutine;

FIG. 26 is a flow chart illustrating an exposure calculation subroutine;

FIG. 27 is a graph illustrating a relationship between the time and thevoltage of a power source upon starting of a motor which is controlledby the circuit of the motor controlling system of FIG. 23;

FIG. 28 is a circuit diagram showing detailed construction of a batterychecking circuit of the circuit of FIG. 23;

FIG. 29 is a flow chart illustrating a battery checking subroutine;

FIG. 30 is a flow chart illustrating a winding subroutine;

FIG. 31 is a circuit diagram showing detailed construction of a motordriving circuit of the circuit of FIG. 23;

FIG. 32 is a flow chart illustrating a motor stopping subroutine;

FIG. 33 is a flow chart illustrating a timer interrupt routine;

FIG. 34 is a flow chart illustrating a motor control II subroutine;

FIG. 35 is a flow chart illustrating an interrupt routine;

FIG. 36 is a flow chart illustrating a motor control I subroutine;

FIG. 37 is a flow chart illustrating a modified winding subroutine;

FIG. 38 is a flow chart illustrating a modified motor control Isubroutine;

FIG. 39 is a graph illustrating a relationship between the time and thevoltage of a power source upon starting of a dc motor where the motor iscontrolled by a modified motor controlling system according to thepresent invention;

FIG. 40 is a circuit diagram showing part of an electric circuit of themodified motor controlling system which attains the relationship of FIG.39;

FIG. 41 is a flow chart illustrating a winding subroutine of operationof the circuit of FIG. 40;

FIG. 42 is a circuit diagram showing a modified form of the circuit ofFIG. 40;

FIG. 43 is a flow chart illustrating a winding subroutine of operationof the circuit of FIG. 42;

FIG. 44 is a perspective view of a film winding and rewinding mechanismof a camera showing a second embodiment of motor controlling system ofthe invention;

FIG. 45 is a block diagram showing an electric circuit of the motorcontrolling system of FIG. 44;

FIG. 46 is a flow chart illustrating a modified winding subroutine ofoperation of the electric circuit of FIG. 45;

FIG. 47 is a flow chart illustrating a counter interrupt subroutine;

FIG. 48 is a flow chart illustrating a timer reading subroutine;

FIG. 49 is a flow chart illustrating a timer interrupt routine ofoperation of the electric circuit of FIG. 45;

FIG. 50 is a perspective view of a film winding and rewinding mechanismof a camera showing a modification to the embodiment of FIG. 44;

FIG. 51 is a circuit diagram showing an equivalent circuit of arotational speed detecting device of the mechanism of FIG. 50;

FIG. 52 is a perspective view of a film winding and rewinding mechanismof a camera showing a third embodiment of motor controlling system ofthe invention;

FIG. 53 is a transverse sectional view of a dc motor which is used todrive the film winding and rewinding mechanism of FIG. 52;

FIG. 54 is a bottom plan view of the motor of FIG. 53;

FIG. 55 is a longitudinal sectional view taken along line E-P-E of FIG.53;

FIG. 56 is a longitudinal sectional view taken along line F-P-F of FIG.53;

FIG. 57 is a fragmentary perspective view of part of the motor of FIG.53 as viewed from the bottom side;

FIG. 58 is a longitudinal sectional view of a dc motor showing a fourthembodiment of motor controlling system of the invention;

FIG. 59 is a transverse sectional view of the motor of FIG. 58 showing acentrifugal switch at a normal inoperative position;

FIG. 60 is a similar view but showing the centrifugal switch at anactuated operative position;

FIG. 61 is a diagrammatic representation illustrating electricconnection of the motor of FIG. 58;

FIG. 62 is a longitudinal sectional view of a dc motor showing a fifthembodiment of motor controlling system of the invention;

FIG. 63 is a transverse sectional view of the motor of FIG. 62 showing amodified centrifugal switch at a normal inoperative position;

FIG. 64 is a similar view but showing the modified centrifugal switch atan actuated operative position;

FIG. 65 is a bottom plan view of a rotary disk of the motor controllingsystem of FIG. 62;

FIG. 66 is a circuit diagram showing an modified electric circuit of themotor controlling system of FIG. 62; and

FIG. 67 is a flow chart illustrating a winding subroutine of the motorcontrolling system of FIG. 62.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is illustrated a concept of a dc motorof the present invention. The dc motor shown is generally denoted at Mand includes a first coil R₁ and a second coil R₂ wound on an iron corewhich will be hereinafter described. The first coil R has a firstterminal T₁ and a second terminal T₂ while the second coil R₂ has athird terminal T and a fourth terminal T₄ Here, the second terminal T₂and the third terminal T₃ are connected to each other and thus treatedas a single common terminal T₂₃.

A dc power source V has an output terminal connected to the fourthterminal T₄ and another output terminal connected to a switch Sw whichserves as a change-over means. The switch Sw can be alternativelyconnected to a contact t₁ connected to the first terminal T₁ and anothercontact t₂ connected to the common terminal T₂₃. Accordingly, in a firstcondition in which the switch Sw is connected to the contact t₁, avoltage is applied between the first terminal T₁ and the fourth terminalT₄, but in a second condition in which the switch Sw is connected to thecontact t₂, a voltage is applied between the common terminal T₂₃ and thefourth terminal T₄.

It is known that following expressions stand for a dc motor:

    V=(R+r)I+K.sub.1 φN                                    (1)

    T=K.sub.2 φ-T.sub.0                                    (2)

Here, V is a voltage of the dc power source V, T a torque produced bythe motor M, r an internal resistance of the dc power motor source V, Ran internal resistance of the motor M, N a rotational frequency of themotor M, φ a magnetic flux of a stator of the motor M, T₀ a no-loadtorque, I electric current flow through the motor M, and K₁ and K₂ areproportional constants which are determined in accordance with a numberof wound turns of the coils. It is to be noted that the no-load torqueoriginates from a bearing loss of the motor M and accordingly I≠0 evenwhere T=0.

Here, it is assumed that the voltage V and the internal resistance r ofthe power source, the stator flux φ and the no-load torque T₀ areconstant and internal resistances of the first and second coils R₁, R₂are represented as R₁, R₂, respectively. Thus, if the switch Sw isconnected to the contact t₂, then R=R₂, and a starting torque Tα in thiscondition will be examined below. Since N=0, the expressions (1) and (2)are rewritten as

    V=(R.sub.2 +r)Iα                                     (3)

    Tα=(K.sub.2)αφI-T.sub.0                    (4)

and accordingly, ##EQU1## It is to be noted here that Iα and (K₂)αrepresent a value of electric current flow through the motor M and avalue of the proportional constant K₂ where the switch Sw is connectedto the contact t₂.

Now a rotational frequency Nα where T=-T₀ is examined here. Since I=0 inthis instance,

    V=(K.sub.1)αφNα                            (6)

and hence ##EQU2##

From tα and Nα which are determined by the expressions (5) and (7),respectively, a characteristic line (T-N)α as shown in FIG. 2 can bedrawn which indicates a relationship between the torque and therotational frequency of the motor M where the switch Sw is connected tothe contact t₂.

Subsequently, another condition in which the switch Sw is connected tothe contact t₁ will be examined. In this case, R=R₁ +R₂. Thus, astarting torque Tβ and a rotational frequency Nβ of the motor M will becalculated.

At first, N=0 is used in the same procedure. Consequently,

    V=(R.sub.1 +R.sub.2 +γ)Iβ                       (8)

    T=(K.sub.2)βφIβ-T.sub.0                      (9)

are obtained, and accordingly, ##EQU3## is obtained. Here, Iβ and (K₂)βrepresent electric current flow through the motor M and a proportionalconstant K₂, respectively, when the switch Sw is connected to thecontact t₁.

Here, if it is assumed that the two coils R₁, R₂ have a same wirediameter, the proportional constants K₁, K₂ vary in proportion toindividual resistances of the coils R₁, R₂. Accordingly, ##EQU4## isobtained, and hence ##EQU5## is obtained. Further, if T=-T₀ is used,##EQU6## is obtained because I=0. Here, the value (K₁)β of theproportional constant K₁ when the switch Sw is connected to the contactt₁ is also proportional to the number of wound turns of the coils of themotor M. Accordingly, ##EQU7## is obtained, and hence ##EQU8## isobtained. Accordingly, from the expressions (5) and (12), ##EQU9## isobtained, and accordingly, a following expression (17) stands:

    Tβ>Tα                                           (17)

Further, from the expressions (7) and (15), ##EQU10## is obtained.Accordingly, a following expression (19) stands:

    Nα>Nβ                                           (19)

Here, from the expressions (16) and (18), another characteristic line(T-N)β where R=R₁ +R₂ can be drawn as shown in FIG. 2 relative to thecharacteristic line (T-N) where R=R₂. Thus, it can be seen from FIG. 2that the characteristic line (T-N)α and the characteristic line (T-N)βintersect each other.

It is to be noted that, in drawing other characteristic lines (T-I)α and(T-I)β as shown in FIG. 2 which indicate an electric current flow and atorque where R= R₂ and R=R₁ +R₂ respectively, since starting torques Tα,Tβ and electric current values Iα, Iβ upon starting of the motor M canbe obtained, a point of coordinates (T=Tα, I=Iα) and (T=Tβ, I=Iβ) andanother point of coordinate (T=-T₀, N=0) must only be interconnected bystraight lines, respectively.

Now, the present invention will be described in detail in connectionwith preferred embodiments thereof. At first, mechanical construction ofa dc motor according to a first embodiment of the invention will bedescribed with reference to a fragmentary perspective view of FIG. 3.The dc motor shown is constituted as a 2-pole 3-slot motor and includesa motor body surrounded by a cylinder 2, an upper cover 4 and a lowercover 6. A pair of permanent magnets 8a, 8b are secured at symmetricalpositions on an inner wall of the cylinder 2 relative to an axis X ofrotation of the motor by suitable means such as application or adhesion.The permanent magnets 8a, 8b have a substantially semicircular shape inplan and are magnetized in a direction of the thickness thereof. An ironcore 10 is supported for rotation around the motor axis X by means ofthe upper cover 4 and the lower cover 6 in a manner hereinafterdescribed and thus serves as a rotor of the motor. The iron core 10 hasthree arms 10a, 10b, 10 c formed in a rotationally symmetricalrelationship with respect to the motor axis X, and a center bore 10dformed at the center thereof. Accordingly, the arms 10a, 10b, 10c of theiron core 10 are spaced apart from each other by an angle of 120degrees. First coils R₁ a, R₁ b, R₁ c and second coils R₂ a, R₂ b,R₂ care wound in a radially juxtaposed relationship from the motor axis X onthe area 10a, 10b, 10c, respectively, of the iron core 10.

Meanwhile, a pair of brushes B₁ a, B₁ b are secured to the upper cover 4while another pair of brushes B₂ a, B₂ b are secured to the lower cover6. In order to allow mounting of the brushes on the lower cover 6, apair of grooved projections 6a, 6b are formed on an inner wall of thelower cover 6, and the brushes B₂ a, B₂ b are thus secured to thegrooved projections 6a, 6b, respectively, by interference fit or thelike. Also in order to allow mounting of the brushes B₁ a, B₁ b on theupper cover 4, another pair of grooved projections 4a, 4b are formed onan inner wall of the upper cover 4 as seen from the bottom plan view ofthe upper cover 4 of FIG. 4, and thus the brushed B₁ a, B₁ b are securedto the grooved projections 4a, 4b, respectively, by interference fit orthe like.

A motor shaft 12 extends through the center bore 10d of the iron core 10and is supported for rotation in center holes 4c, 6c formed in the upperand lower covers 4, 6, respectively. The iron core 10 is secured in anintegral relationship to the motor shaft 12.

An electrode 14 is integrally mounted on the iron core 10 for contactingengagement with the brushes B₂ a, B₂ b on the lower cover 6 and servesas a commutator. The electrode 14 has a center bore 14a formed thereinand an insulating zone 14b formed thereon, and the motor shaft 12extends through the center bore 14a of the electrode 14. Three electrodesections S₂ ab, S₂ bc, S₂ ca are formed in a rotationally symmetricalrelationship around the motor axis X on an outer periphery of theelectrode 14. Another electrode 16 is integrally mounted on the ironcore 10 for contacting engagement with the brushes B₁ a, B₁ b on theupper cover 4 and serves similarly as a commutator. Also the electrode16 has a center bore 16a formed therein and an insulator section 16bformed thereon, and the motor shaft 12 extends through the center bore16a of the electrode 16. The electrode 16 further has three electrodesections S₁ ab, S₁ bc, S₁ ca formed in a rotationally symmetricalrelationship around the motor axis X on an outer periphery thereof. Thethree electrode sections S₁ ab, S₁ bc, S₁ ca of the electrode 16 and thepair of brushes B₁ a, B₁ b on the upper cover 4 have such a relationshipas seen in FIG. 4, and the three electrode sections S₂ ab, S₂ bc, S₂ caof the electrode 14 and the pair of brushes B₂ a, B₂ b have a similarrelationship therebetween.

Referring back to FIG. 3, a pair of spacers 18, 20 are interposedbetween the iron core 10 and the electrodes 14, 16, respectively. Thespacers 18, 20 are provided to assure spacings for allowing a wire topass therethrough when the coils are wound on the iron core 10.Accordingly, the electrode 14, the spacer 18, the iron core 10, theother spacer 20 and the other electrode 16 are integrally secured in theorder as listed from below to the motor shaft 12 by a suitable methodsuch as interference fit. Accordingly, the motor components listed justabove are rotated in an integral relationship with the motor shaft 12.

A transverse sectional view of the motor of the embodiment as viewedfrom the position of the upper cover 4 is shown in FIG. 5 while alongitudinal sectional view taken along line Y-A-B-O-C-D-Y in FIG. 5 isshown in FIG. 6. Here, the upper and lower portions of FIG. 6corresponds also to a longitudinal sectional view taken along line Z-O-Zin FIG. 4. As illustrated in FIG. 5, the permanent magnets 8a, 8b aremagnetized in a diametrical direction relative to the motor axis X (in adirection of the thickness). Further, a perspective view of the motorbody of the present invention is shown in FIG. 7. As apparently seenfrom FIG. 7, in the present embodiment, three input leads L₁, L₂, L₃ areall drawn out from the upper cover 4. Thus, in order to assure wiringsfor power supply to the pair of brushes B₂ a, B₂ b mounted on the lowercover 6, two dead spaces DS₁, DS₂ defined by the cylinder 1, the ironcore 10 and the permanent magnets 8a, 8b are utilized to thread the leadL₃ and an additional lead L₂ ' which will be hereinafter described.

Now, electric connection of the motor of the embodiment will bedescribed. Referring back to FIG. 3, the first coils R₁ a, R₁ b, R₁ ceach have a pair of upwardly extending terminals l₁ a, l₁ b, l₁ c,respectively, while the second coils R₂ R₂ b, R₂ c each have a pair ofupwardly extending terminal l₂ a, l₂ b, l₂ c, respectively. As seen froma schematic representation of FIG. 8, one of the pair of terminals l₁ aof the first coil R₁ a is connected to the electrode S₁ ab while theother terminal l₁ a is connected to the electrode S₁ ca. One of thesecond pair of terminal l₁ b of the first coil R₁ b is connected to theelectrode S₁ ab and the other terminal l₁ b is connected to theelectrode S₁ bc. Further, one of the other pair of terminals l₁ c of thefirst coil R₁ c is connected to the electrode S₁ bc and the otherterminal l₁ c is connected to the electrode S₁ ca.

Meanwhile, one of the pair of terminals l₂ a of the second coil R₂ a isconnected to the electrode S₂ ab while the other terminal l₂ a isconnected to the electrode S₂ ca. One of the second pair of terminals l₂b of the second coil R₂ b is connected to the electrode S₂ ab and theother terminal l₂ b is connected to the electrode S₂ bc. Further, one ofthe other pair of terminals l₂ c of the second coil R₂ c is connected tothe electrode S₂ bc and the other terminal l₂ c is connected to theelectrode S₂ ca.

Further, the brush B₁ a secured to the upper cover 4 is electricallyconnected to the brush B₂ b secured to the lower cover 6 via the lead L₂' extending through the above described dead space DS₁ shown in FIG. 5.On the other hand, the lead L₁ is electrically connected to the brush B₁b secured to the upper cover 4 and extends externally of the motor body.Meanwhile, the lead L₃ is electrically connected to the brush B₂ asecured to the lower cover 6 and extends externally through the deadspace DS₂ shown in FIG. 5. Then, ends of the leads L₁, L₂, L₃ correspondto the terminal T₁, T₂₃, T₄, respectively, shown in FIG. 1.

It is to be noted that, in the first embodiment described above, thefirst coils R₁ a, R₁ b, R₁ c and the second coils R₂ a, R₂ b, R₂ c aremounted in a juxtaposed relationship in a diametrical direction from themotor axis X on the three arms 10a, 10b, 10c of the iron core 10 whichserves as a rotor. However the present invention is not limited to sucha specific arrangement of the embodiment, and various alternations andmodifications can be made to the same.

Such modifications are shown in FIGS. 9 to 20, and it is to be notedthat in those figures, like parts or components are denoted by likereference symbols to those of the first embodiment shown FIGS. 3 to 8.In particular, in a second embodiment shown in a longitudinal sectionalview of FIG. 9 and a transverse sectional view of FIG. 10, first coilsR₁ a, R₁ b, R₁ c and second coils R₂ a, R₂ b, R₂ c are mounted in anoverlapping relationship in a direction of the thickness of the arms10a, 10b, 10c, respectively. Meanwhile, in a third embodiment shown in alongitudinal sectional view of FIG. 11 and a transverse sectional viewof FIG. 12 taken along line XII--XII (XII'--XII') of FIG. 11, three arms10a, 10b, 10c of an iron core 10 are each formed into two separatesections extending in a direction parallel to the motor axis X, andfirst coils R₁ a, R₁ b, R₁ c are mounted on the upper arm sections whilesecond coils R₂ a, R₂ b, R₂ c are mounted on the lower arm sections. Inthe third embodiment, in order to allow the first and second coils to bearranged in an overlapping relationship in a direction parallel to themotor axis X, a spacer 22 may be interposed between the upper and lowersections of the arms 10a , 10b, 10c.

Further, while in the first embodiment described hereinabove the covers4, 6, the electrodes 14, 16 and the brushes B₁ a, B₁ b, B₂ a, B₂ b aredisposed above and below the iron core 10, respectively, a fourthembodiment shown in a longitudinal sectional view of FIG. 13 is modifiedsuch that a cylinder 2 is formed in an integral relationship with alower cover while emitting the lower cover 6 of the first embodiment asa separate component, and two electrodes 14, 16 and two pairs of brushesB₁ a, B₁ b, B₂ a, B₂ b are located only on an upper cover 4 above aniron core 10. Thus, in order to prevent the two electrodes 14, 16located above the iron core 10 from contacting with each other, aseparate spacer 24 is interposed between the electrodes 14, 16. Sixterminals l₁ a, l₁ b, l₁ c extending upwardly from first coils R₁ a, R₁b, R₁ c located adjacent a motor shaft 12 extend through through-holes26a, 26b, 26c, respectively, formed on a support ring 26 on which theelectrode 14 is supported and the connected to the electrode 16. Atransverse sectional view taken along line XIV--XIV of FIG. 13 is shownin FIG. 14. Thus leads may be easily individually drawn externally fromthe two pairs of brushes B₁ a, B₁ b, B₂ a, B₂ b located above the ironcore 10 so as to provide the motor with four input terminals as seen inFIG. 13.

Electrical connection of the dc motor which has four input terminals isshown in a diagrammatic representation of FIG. 15. In particular, in thefourth embodiment, a lead L₂ is connected to the brush B₁ a, anotherlead L₁ to the brush B₁ b, a further lead L to the brush B₂ a, and astill further lead L₂ ' to the brush B₂ b. The four leads L₁, L₂, L₂ ',L₃ are extended externally from the upper cover 4. Accordingly, an endof the lead L₁ shown in FIG. 15 corresponds to the terminal T₁ of FIG.1, an end of the lead L₂ to the terminal T₂, an end of the lead L₂ ' tothe terminal T₃, and an end of the lead L₃ to the terminal T₄.

Further, while in the fourth embodiment shown in FIG. 13 the twoelectrodes 14, 16 are located at different positions along a directionof the motor axis X, the present embodiment is not limited to thespecific arrangement, and the two electrodes 14, 16 may be arranged inan overlapping relationship one around the other as shown in alongitudinal sectional view of FIG. 16 in which a fifth embodiment isshown. Referring to FIG. 16, the upper electrode 16 extends downwardlythrough the lower electrode 14, and an insulator ring 28 is interposedbetween the electrodes 14, 16 in order to prevent the electrodes 14, 16from contacting with each other. Accordingly, the lower electrode 14 hasa through-hole 16h formed therein for allowing the insulator ring 28 andthe upper electrode 16 to extend therethrough. A transverse sectionalview taken along line XVII--XVII of FIG. 16 is shown in FIG. 17.

Further, while in the first embodiment the leads L₂ ', L₃ connected tothe lower brushes B₂ a, B₂ b are threaded through the dead spaces DS₁,DS₂ so that all the leads may be drawn out from the upper cover 4, asixth embodiment shown in a longitudinal sectional view of FIG. 18 isconstituted such that lower brushes B₂ a, B₂ b are connected to leadswhich extend downwardly through a lower cover 6. Such a constructionwill facilitate assembly of a dc motor because there is no necessity tothread leads through dead spaces such as the dead spaces DS₁, DS₂ of thefirst embodiment in order to connect the leads to brushes. Here, such aconstruction that some of a plurality of leads are drawn out from anupper cover while the remaining leads are drawn out from a lower coveras in the sixth embodiment can be applied not only to the firstembodiment but also to any of the second to fifth embodiments describedhereinabove.

In addition, while in all of the first to sixth embodiments of dc motorof the present invention the first and second coils are wound separatelyon the iron core, they may otherwise be wound in an unseparablerelationship to each other on the iron core. Such a modification isillustrated in a partial longitudinal sectional view of FIG. 19 andtransverse sectional view of FIG. 20. Referring to FIGS. 19 and 20, twoassociated coils such as first and second coils R₁ a, R₂ a are woundsuch that wound turns of conductors thereof are arranged in an alternaterelationship in a diametrical direction of the motor shaft. In assemblyof the coils, a set of two conductors may be wound simultaneously in ajuxtaposed relationship around an arm such as an arm 10a of the ironcore 10. This arrangement of the coils is advantageous in that it willmake the turn ratio of a motor constant and will reduce fluctuationsamong individual motors in output power, that is, in relationshipbetween the torque and the rotational frequency or speed.

Further, while in all of the embodiments described hereinabove leads areconnected to brushes within a motor body, the present invention is notlimited to the specific construction, and thus leads may be connected,outside a motor body, to ends of brushes extended externally from themotor body.

Now, a motor controlling system according to the present invention whichcan efficiently control any of the dc motors of the precedingembodiments described above will be described in connection withpreferred embodiments thereof. A first embodiment of motor controllingsystem of the invention is shown in FIG. 21 wherein the motorcontrolling system is applied to a film winding and rewinding mechanismof a camera.

At first, a film winding operation after photographing will be describedwith reference to FIG. 21. If a shutter not shown moves and thusexposure of a film frame is completed, an exposure completion signallever 20 pushes a winding stopping lever 22 to pivot in a counterclockwise direction in FIG. 21 so that a projection 22a on the windingstopping lever 22 is moved out of engagement with a recess 24a formed ina winding stopping cam 24. Meanwhile, the counterclockwise pivotalmotion of the winding stopping lever 22 in FIG. 21 closes a microswitchS₆ thereby to cause a motor M to be driven to rotate in acounterclockwise direction (forward direction) in FIG. 21. A gear 28 iscoupled to a motor shaft 26 of the motor M and is held in meshedengagement with a large gear 30a of a speed reduction gear member 30.The speed reduction gear member 30 further includes a small gear 30bmounted for integral rotation with the large gear 30a, and a planetarygear 34 is held in meshed engagement with the small gear 30b. Theplanetary gear 34 is supported for rotation on a planetary gear lever 32which is in turn supported for rotation in a coaxial relationship withthe speed reduction gear member 30. The planetary gear 34 is anotherspeed reduction gear member 36 but is not necessarily meshed with thelarge gear 36a immediately after a motion of the shutter. Thus, as themotor M rotates in the counterclockwise direction to rotate the speedreduction gear member 30 in the clockwise direction, the planetary gearlever 32 which frictionally engages with an upper face of the speedreduction gear member 30 is also rotated in the clockwise direction sothat the planetary gear 34 thereon is brought into meshed engagementwith the large gear 36a of the speed reduction gear member 36. The speedreduction gear member 36 is connected to a sprocket gear 42 via afurther gear 38 and a drive gear 40 so that as the planetary gear 34 isrotated in the counterclockwise direction and is meshed with the largegear 36a of the speed reduction gear member 36, the sprocket gear 42 isrotated in the counterclockwise direction. The sprocket gear 42 is heldin meshed engagement with a winding stopping gear 44 which is mountedfor integral rotation with the winding stopping cam 24. Thus, since herethe recess 24a of the winding stopping cam 24 is out of engagement withthe projection 22a of the winding stopping lever 22 and hence rotationof the winding stopping cam 24 and the winding stopping gear is allowed,rotation of the sprocket gear 42 in the counterclockwise directionrotates a spool gear 46 in the counterclockwise direction via thewinding stopping gear 44.

The spool gear 46 is connected to a spool 48 via a spool friction spring46a. Thus, a film is wound by counterclockwise rotation of the spool 48and a sprocket connected to the sprocket gear 42.

Upon completion of winding of a film by one frame, the projection 22a ofthe winding stopping lever 22 is again brought into engagement with therecess 24a of the winding stopping cam 24 which is thus rotated by onecomplete rotation for winding of the film by one frame, and as thewinding stopping lever 22 is thereupon pivoted in the clockwisedirection, the microswitch S₆ is opened by the same to stop the motor M,thereby completing the winding of the film by one frame. It is to benoted that the exposure completion signal lever 20 is returned to itsinitial position in response to charging of a shutter mechanism notshown which is charged by an additional gear connected to the motor M.

Now, a film rewinding operation which is performed after completion ofphotographing of all the available frames of a film will be described.When the entire camera is brought into a halted condition aftercompletion of photographing of an entire film, the sprocket 50 and thespool 48 are also halted. Then, if the halted condition continues for apredetermined interval of time or more, an interrupt signal is deliveredto a controlling device for the motor M so that driving of the motor Mis stopped in order to allow subsequent starting of a rewindingoperation for the film.

Rewinding of the film is started by pushing a rewinding operating lever52 in a direction of an arrow mark of FIG. 21. As the rewindingoperating lever 52 is pushed in this manner, the winding stopping lever22 is pivoted thereby in the counterclockwise direction in FIG. 21 sothat it is brought out of engagement with the winding stopping cam 24.In this instance, another microswitch S₇ is closed by the operatinglever 52 so that the motor controlling device enters a film rewindingroutine which will be described hereinafter in detail.

In response to closing of the microswitch S₇, the motor M is rotated nowin a rewinding direction (clockwise direction in FIG. 21) opposite tothe film winding direction (counterclockwise direction in FIG. 21).Consequently, the speed reduction gear member 30 is rotated in thecounterclockwise direction, and the planetary gear lever 32 is rotatedalso in the counterclockwise direction around the speed reduction gearmember 30. As a result of such counterclockwise rotation of theplanetary gear lever 32, a rewinding planetary gear 54 supported on theplanetary gear lever 32 is brought into meshed engagement with arewinding gear 56. The rewinding gear 56 is connected to a rewindingpulley 60 via a gear 58 so that as the rewinding planetary gear 54 isrotated in the clockwise direction and is meshed with the rewinding gear58, the pulley 60 is rotated in the clockwise direction.

The pulley 60 is connected by a timing belt 62 to a rewinding forkpulley 64 secured to a rewinding fork 66 so that as the pulley 60 isrotated in the clockwise direction, the rewinding fork 66 is rotatedalso in the clockwise direction. The rewinding fork 66 thus attempts tomesh with a rotatable shaft of a film cartridge not shown and rotate thesame in the clockwise direction to wind up the film into the cartridge.Here, since the winding stopping cam 24 is already out of engagementwith the winding topping lever 22, the spool 48 around which the film ispartially wrapped and the sprocket 50 are allowed to rotate in theclockwise direction. Accordingly, when the film is wound up into thecartridge, the sprocket 50 and the spool 48 are drawn by the film andthus rotated in the clockwise direction by the latter.

Upon completion of the rewinding operation, it is detected by a filmdetecting switch not shown and driving of the motor M is thus stopped.It is to be noted that the rewinding operating lever 52 is automaticallyreturned to its initial position when a rear cover of the camera notshown is opened.

The shutter mechanism is energized by a mechanism shown in FIG. 22.Referring to FIG. 22, a gear 68 is held mounted on the sprocket 50 andhas a cam 70 formed on an upper face thereof. Thus, as the sprocket 50is rotated in the counterclockwise direction in FIG. 22 for winding of afilm by one frame, the gear 68 is rotated in the clockwise direction inan integral relationship with the cam 70 thereon. Upon such rotation ofthe cam 70, a cam follower 72a securely mounted on a lever 72 is pushedby the cam 70 to pivot the lever 72 in the clockwise direction (in adirection of an arrow mark A) around an axis P. As the lever 72 ispivoted in the direction A, another lever 74 is also pivoted in thedirection A thereby to energize the shutter mechanism not shown.

An electric circuit of the motor controlling system according to theinvention described above is shown in FIG. 23. Referring to FIG. 23, thecircuit shown includes a power source battery E, and a microcomputer μCfor executing sequencing control and exposure calculation of the entirecamera. The microcomputer μC is connected to the power source E via adiode D₁ so that power may be supplied thereto from the power source E.The circuit further includes a photometry circuit LM for receiving lighttransmitted through a photographing lens not shown to measure abrightness of an object, an automatic film sensitivity reading circuitISO for automatically reading a sensitivity of a film loaded in thecamera, and an open F-number reading circuit AV for reading an openF-number of a photographing lens mounted on the camera body. Thosecircuits LM, ISO, AV are connected to deliver signals Bvo, Sv, Avo ofdigital A.P.E.X. values as output information to the microcomputer μC.

The circuit shown in FIG. 23 further includes an exposure controllingcircuit AE for controlling operation of an aperture diaphragm and ashutter in response to an aperture value signal Av and a shutter speedvalue signal Tv delivered from the microcomputer μC. The circuit furthercomprises a battery checking circuit BC for checking an electric currentand a voltage when a current is flowed through a resistor correspondingto an actual load. Thus, the microcomputer μC judges in accordance witha checked voltage value from the battery checking circuit BC whether ornot change-over between the coils of the motor M is to be allowed. Thecircuit further includes a motor controlling circuit MC for decoding a3-bit controlling signal delivered from the microcomputer μC to producea controlling signal to be delivered to a motor driver circuit MD fordriving the motor M. Those circuits AE, BC, MC, MD are all connected tothe power source E via a power supply transistor Tr₁ so that power maybe supplied to the circuits from the power source E. Here, the base ofthe power supply transistor Tr₁ is connected to an output terminal Pwcof the microcomputer μC via an inverter IN₁ so that supply of power tothe circuits AE, BC, MC, MD may be controlled by the microcomputer μC. Aresistor Rr and a capacitor Cr are connected to an input terminal RE ofof the microcomputer μC and produces a reset signal to be delivered tothe input terminal RE of the microcomputer μC when a battery is set inposition in the camera.

The circuit shown in FIG. 23 includes various switches including aphotographing preparing switch S₁ which is turned on by depression of ashutter release button not shown to a first extent or depth. Uponturning on of the switch S₁, a signal which changes from a high ("H")level to a low ("L") level is delivered to an interrupt terminal INT₁ ofthe microcomputer μC, and consequently an interrupt routine "INT₁ "which will be hereinafter described will be executed by themicrocomputer μC. A release switch S₂ is turned on by depression of theshutter release button to a second extent or depth which is greater thanthe first extent or depth, and exposure controlling operation is thusinitiated in response to turning on of the release switch S2. A rearcover closed switch S₃ is turned on when a rear cover of the camera isclosed, and upon turning on of the rear cover closed switch S₃, a signalchanging from an "H" level to an "L" level is delivered to anotherinterrupt terminal INT₂ of the microcomputer μC, and consequently themicrocomputer μC executes an interrupt routine "INT₂ " which will behereinafter described. A manually selecting switch S₄ is turned on oroff by manual selecting operation thereof between an automaticchangeover mode wherein the driving speed of the motor M is changed overautomatically and a low speed mode wherein the driving speed of themotor M is compulsorily set to a low driving speed. The switch S₄ isconstituted such that it is off for the automatic change-over mode andon for the low speed mode.

A film detecting switch S₅ is located at a film magazine receivingportion of a camera body in an opposing relationship to a plane alongwhich a film travels for detecting a film drawn out from the filmcartridge. An exposure completion switch S₈ is turned on upon completionof movement of trailing curtain of a focal plane shutter by completionof exposure operation and is turned off by a mechanism not shown when afilm is wound by one frame. A one frame winding completion detectingswitch S₆ corresponds to the microswitch S₆ of FIG. 21 and is thusturned on upon starting of winding of a film and then tuned off uponcompletion of the winding of the film by one frame. A rewinding switchS₇ corresponds to the microswitch S₇ of FIG. 21 and is thus closed bydepression of the rewinding operating lever 52 in order to effectrewinding of a film.

Now, operation of the camera having the construction described abovewill be described with reference to flow charts shown in severalfigures. If a battery E is first mounted in position in the camera, areset signal which changes from an "L" level to an "H" level isdelivered to the reset terminal RE of the microcomputer μC.Consequently, the microcomputer μC enters a reset routine "RESET" ofFIG. 24 which illustrates general operation of the microcomputer μC.Referring to FIG. 24, at first at step #1, the microcomputer μCinitializes internal flags at step #2, the microcomputer μC changesoutput terminals OP₁, OP₂ to an "L" level. After then, the microcomputerμC enables, at step #3, interruption thereof by an interrupt signalwhich is to be received at either of the interrupt terminals INT₁, INT₂,and then at step #4, it stops operation of itself and enters a haltedstate.

In this condition, the shutter release button not shown may bedepressed. Thus, when the shutter release button is depressed to thefirst extent or depth, the photographing preparing switch S₁ is turnedon so that a signal changing from the "H" level to the "L" level isdelivered to the interrupt terminal INT₁ of the microcomputer μC.Consequently, the microcomputer μC executes the interrupt routine "INT₁". In the interrupt routine "INT₁ ", the microcomputer μC inhibits, atfirst at step #5, interruption for execution of the interrupt routine"INT₁ ", and then at step #6, it turns the power, supply transistor Tr₁on in order to start supply of power to the exposure controlling circuitAE, the battery checking circuit BC, the motor controlling circuit MCAND THE MOTOR DRIVING CIRCUIT MD via a power supply line V₁ (refer toFIG. 23). Then at step #7, the microcomputer μC determines whether ornot the photographing preparing switch S₁ is on, and in case the switchS₁ is not on, the microcomputer μC turns the power supply transistor Tr₁off at step #8 and the advances the program to step #3.

To the contrary, in case the photographing preparing switch S₁ is on atstep #7, exposure information is received at step #9 and thencalculations for exposure are performed at step #10. Flow charts ofsubroutines illustrating detailed operations of the steps #9 and #10 areshown in FIGS. 25 and 26, respectively. At first, in the exposureinformation reading routine of FIG. 25 illustrating detailed operationof step #9, film sensitivity information (speed value) Sv is read atstep #9-1 from the automatic film sensitivity reading circuit ISO, andthen at step #9-2, open F-number value information (aperture value) Avois read from the open F-number value reading circuit AV. Then at #9-3,the microcomputer μC reads from the photometry circuit LM information(luminance value) Bvo regarding a brightness of an object measured fromlight passing through the photographing lens and received by thephotometry circuit LM. After then, the program returns to the routine ofFIG. 24.

Meanwhile, in the exposure calculation subroutine of FIG. 26illustrating detailed operation of step #10, at first an exposure valueEv is calculated at step #10-1 from the photographing information Sv,Avo, Bvo read at step #9, and then at step #10-2, a controlling aperturevalue Av and a controlling shutter speed (time value) Tv are calculatedfrom the exposure value Ev in accordance with a predetermined programchart not shown, whereafter the program returns to the routine of FIG.24.

Referring back to FIG. 24, after completion of the operations of steps#9 and #10 illustrated in FIGS. 25 and 26, the microcomputer μC checksat step #11 whether or not the shutter release button is depressed tothe second extent or depth to turn the release switch S₂ on, and if theshutter release button is not depressed to the extent, the programreturns to step #7. On the contrary, in case the shutter release buttonis depressed to the extent, the program advances to step #12 at whichthe microcomputer μC executes exposure controlling operation. Then atstep #13, the microcomputer μC waits until after completion of theexposure controlling operation. Thus, after movement of the trailingcurtain of the shutter to complete the exposure controlling operation, afilm must subsequently be wound by one frame. However, in the presentembodiment, it is detected at step #14 before such film windingoperation whether the motor M is in the automatic changeover mode or inthe low speed high torque rotation mode. Here at step #14, themicrocomputer μC determines from the state of the manually selectingswitch S₄ whether or not the low speed high torque rotation mode isselected, and then where the low speed high torque rotation mode isselected, the program advances to step #15 at which an auto flag AUTOFindicating the automatic change-over mode is reset to zero. On thecontrary, where the automatic change-over mode is selected, the programadvances to step #16 at which a battery checking subroutine is executedfor determining whether or not the battery E can stand power consumptionupon high speed rotation of the motor M by energizing a resistorcorresponding to a load of the motor M and by measuring a voltage dropacross the resistor.

In prior to description of detailed construction of the battery checkingcircuit which actually checks the power source battery and of flowcharts illustrating battery checking operation of the battery checkingcircuit, a relationship between a driving speed of the motor and avoltage of the battery will be described. Reference is now had to agraph of FIG. 27 wherein the axis of abscissa indicates a time forfeeding a film and the axis of ordinate indicates a voltage of a powersource battery.

At first upon starting of winding of a film, a voltage is applied acrossa serial circuit of the first and second coils in order to attain lowspeed high torque rotation of the motor because a high torque isrequired in order to start winding of the film. This corresponds

switching of the switch Sw to the contact t₁ in FIG. 1 which illustratesa concept of the present invention. Then, after lapse of a predeterminedinterval of time I₁, the motor M is changed over to the high speed lowtorque rotation side. In particular, the switch Sw in FIG. 1 is switchedto the contract t₂. The time I₁ is determined such that the outputrotational frequency of the motor M may reach, within the time I₁, avalue around a point in FIG. 2 at which two characteristic lines (T-N)αand (T-N)β intersect each other. When the motor M is changed over to thehigh speed low torque rotation side in this manner, the voltage maysometimes become lower than that at the time of starting of the lowspeed high torque rotation (particularly where the capacity of thebattery is low) due to the fact that the internal resistance of themotor M reduces comparing with the internal resistance upon low speedhigh torque rotation of the motor M. Here, if the voltage of the powersource reduces, the current torque may not be obtained. Consequently,the film may not be wound as seen from a curve (b) of FIG. 27, whichwill make such change-over of rotation of the motor M to the high speedlow torque rotation side ineffective. Therefore, in the presentembodiment, a predetermined voltage level such as indicated at VR inFIG. 27 is determined in order to obtain a current flow and hence avoltage required to obtain a torque necessary for winding of the film.Thus, in case the power source voltage when the resistor correspondingto the actual load is energized is higher than the predetermined voltagelevel VR, it is considered that the motor M can be driven efficientlyand accordingly the motor M is changed over to the high speed low torquerotation side in order to raise the winding speed of the film. To thecontrary, in case the open voltage is lower than the predeterminedvoltage level VR, the low speed high torque rotation of the motor ismaintained as seen from a curve (c) of FIG. 27 in order to obtain a hightorque to assure winding of the film.

FIG. 28 shows detailed construction of the battery checking circuit BCfor checking a battery, and FIG. 29 illustrates the battery checkingsubroutine of step #16 of FIG. 24. Now, operation of the batterychecking circuit BC will be described with reference to a circuitdiagram of FIG. 28 and a flow chart of FIG. 29. At first at step #16-1of the flow chart of FIG. 29, the microcomputer μC delivers from theoutput terminal OP₂ thereof a power-on reset signal POR whichmomentarily presents an "H" level. Consequently, an RS-type flip-flopRS₁ shown in FIG. 28 is reset. Subsequently at step #16-2, the outputterminal OP₁ of the microcomputer μC is held at the "H" level forseveral milliseconds (for example, 2 to 3 milliseconds) to turn ontransistors Tr₂, Tr₃ shown in FIG. 28 in order to flow an electriccurrent through a resistor R₁ corresponding to a load to the motor M (aload to the motor M upon driving at a high speed). Then at step #16-3,the microcomputer μC determines whether or not a voltage Va obtained bydivision of a voltage when the current is flowed through the resistor R₁is lower than a predetermined reference voltage Vr₁ of a referencevoltage source Vr₁ (which is a voltage corresponding to the voltagelevel VR of FIG. 27). In case the voltage Va is lower than the referencevoltage Vr₁, a comparator COMP₁ delivers a signal changing to an "H"level to set the RS flip-flop RS₁. Consequently, the RS flip-flopproduces an "H" level. To the contrary, in case the divided voltage Vaof the power source voltage is equal to or higher than the referencevoltage Vr₁, the RS flip-flop maintains its reset state and thuscontinues to deliver the "L" level. Accordingly, the "H" level of theoutput of the RS flip-flop RS₁ indicates that the voltage of the powersource has lowered to a voltage lower than the predetermined level, andon the contrary the "L" level indicates that the power source provides asufficiently high voltage to drive the motor at a high speed.

In this manner, the microcomputer μC controls, at step #16-2, thetransistors Tr₂, Tr₃ to turn on and continue its on state for severalmilliseconds and then checks, at step #16-3, output of the RS flip-flopRS₁ in order to check the battery. Then, in case it is determined as aresult of such battery checking that the voltage of the battery issufficiently high, that is, in case the output of the RS flip-flop RS₁is at the "L" level, the auto flag AUTOF indicating the automaticchange-over mode is set to "1" at step #16-4. On the contrary, in caseit is determined at step #16-3 that the output of the RS flip-flop RS₁is not sufficiently high, that is, in case the output of the RSflip-flop RS₁ is at the "H" level, the auto flag AUTOF is reset to "0".After either of the steps #16-4 and #16-5, the program returns to theroutine of FIG. 24.

Referring back again to FIG. 24, after the driving speed of the motor Mhas been selected in this manner, the microcomputer μC controls a filmwinding operation. Referring now to FIG. 30 which shows a subroutineindicating the film winding operation, the microcomputer μC inhibits, atfirst at step #17-1, interruption for execution of the interrupt routineINT₁ by turning on of the photographing preparing switch S₁, and thenenables, at step #17-2, timer interrupt which will be hereinafterdescribed, whereafter a timer I which will be hereinafter described isreset and started at step #17-3. The timer interrupt is provided inorder to perform a film rewinding operation when photographing of aphotographable number of frames of a film is completed and the filmcannot be wound any more. It should be considered here that the timer Iis a hardware timer provided within the microcomputer μC.

here, a relationship between a 3-bit signal (b₂, b₁, b₀) transmittedfrom the microcomputer μC to the motor controlling circuit MC and a6-bit controlling signal (a, b, c, d, e, f) delivered from the motorcontrolling circuit MC to the motor driving circuit MD is illustrated inTable 1 below.

                  TABLE 1                                                         ______________________________________                                        Signal from                                                                   Microcomputer                                                                            Contents of Control Signal                                         b2   b1     b0     Signals   a   b    c   d   e   f                           ______________________________________                                        1    0      0      Low speed L   O    O   H   O   O                                              Forward R.                                                 1    0      1      Low Speed O   H    L   O   O   O                                              Reverse R.                                                 0    1      0      HIGH SPEED                                                                              O   O    O   H   L   O                                              Forward R.                                                 0    1      1      HIGH SPEED                                                                              O   O    L   O   O   H                                              Reverse R.                                                 0    0      1      STOP      O   H    O   H   O   H                           0    0      0      OFF       O   O    O   O   O   O                           0    0      1      STOP      O   H    O   H   O   O                           ______________________________________                                    

In Table 1, a character "L" represents an "L" level, "H" an "H" level,and "O" an open state.

Subsequently at step #17-4 of FIG. 30, a film winding operation isstared. In this instance, however, the microcomputer μC delivers a 3-bitsignal (1, 0, 0) shown in Table 1 to the motor controlling circuit MC inorder to rotate the motor M in a low speed high torque condition at aninitial stage of the film winding operation. Upon reception of the 3-bitsignal, the motor controlling circuit MC delivers a 6-bit signal (L, O,O, H, O, O) as controlling signal (a, b, c, d, e, f) to the motordriving circuit MD.

Here, the motor controlling circuit MC and the motor driving circuit MDwill be described. The microcomputer μC sends a selected one of 6 3-bitsignals to the motor controlling circuit MC in accordance with a manneror mode in which the motor M is to be driven. One of the 6 kinds of3-bit signals are shown in Table 1 above. Thus, where the motor M is tobe driven to rotate in the forward direction at a low speed, themicrocomputer μC delivers a signal of (b₂, b₁, b₀)=(1, 0, 0). As themotor controlling circuit MC receives the signal, it decodes thereceived signal into a 6-bit signal (L, O, O, H, O, O) as a controllingsignal (a, b, c, d, e, f) and delivers the 6-bit signal to the motordriving circuit MD.

The motor driving circuit MD has such a construction as shown in FIG.31. Thus, when the motor M is to be driven to rotate in the forwarddirection in a low speed high torque condition, transistors Tr₄, Tr₇ areboth turned on while the remaining transistors Tr₅, Tr₆, Tr₈, Tr₉ areturned off. Accordingly, electric current flows through the transistorTr₄, the motor M (in a direction of an arrow mark DA) and then thetransistor Tr₇ thereby to drive the motor M to rotate in the forwarddirection in a low speed high torque condition. Similarly, for reverserotation of the motor M in a low speed high torque condition, signalsare (b₂, b₁, b₀)=(1, 0, 1) and (a, b, c, d, e, f)=(O, H, L, O, O,O), andelectric current flows through the transistor Tr₆, the motor M (in adirection of an arrow mark DB) and then the transistor Tr₅ thereby todrive the motor M to rotate in the reverse direction in a low speed hightorque condition. For high speed low torque forward rotation of themotor, signals are (b₂, b₁, b₀)=(0, 1, 0) and (a, b, c, d, e, f)=(O, O,O, H, L, O) and electric current flows through the transistor Tr₈, themotor M and the transistor Tr₇ to drive the motor M in the forwarddirection in a high speed low torque condition. Here, it is to be notedthat a signal line extending from the lower center of the motor M inFIG. 31 is extracted from a tap of the motor M. Finally for high speedlow torque reverse rotation of the motor M, signals are (b₂, b₁, b₀)=(0,1, 1) and (a, b, c, d, e, f)=(O, O, L, O, O, H) and electric currentflows through the transistor Tr₆, the motor M and then the transistorTr₉.

In order to stop the motor M, the NPN type transistors Tr₅, Tr₇, Tr₉ areall turned on to short the entire motor M irrespective of the speed andthe direction of rotation of the motor. The reason is given now. In thecase of rotation of the motor M in a low speed high torque condition,the two coils are both energized, and hence the two coils must naturallybe shorted upon stopping of the motor M. To the contrary, in the case ofrotation at a high speed low torque condition, only one of the two coilsis energized, and accordingly it may seem advisable to short only theenergized coil. However, this is not practically advantageous because ofa following reason. In particular, the two coils are wound on thecoaxial iron core, and accordingly the other coil which is not energizedrotates around the axis of the iron core similarly as the energizedcoil. Consequently, an electromotive force is generated in the coils.This will be described briefly with reference to FIG. 1. It is assumednow that the switch Sw in FIG. 1 is connected to the contact t₂ Thus,since the coils R₁, R₂ are both rotating, a predetermined electromotiveforce (energy) is generated in each of the coils. If supply of power tothe motor M is stopped while the coils are rotating, the motor M willcontinue its rotation for a little while due to its inertia. In thisinstance, if only the coil R₂ is shorted, the motor M iselectromagnetically braked by the coil R₂ while the energy of inertialis consumed to attempt to step rotation of the motor M, but thegenerated energy of the other coil R₁ does not contribute to suchelectromagnetic braking, which may result in failure in production of asufficient braking force to stop the motor M. Accordingly, the shortingonly of the coil R₂ may not cause the motor M to stop its rotationrapidly with a high efficiency. This principle naturally applies alsowhere the motor is rotating in the opposite direction. Therefore, theentire coils are shorted when rotation of the motor M is to be stoppedirrespective of the direction and the speed of rotation of the motor M.In a possible modification, only the transistors Tr₅, Tr₇ may be turnedon in order to attain a similar effect (this is shown in the lowermostline in Table 1 above).

Referring back to the film winding subroutine of FIG. 30, after themicrocomputer μC has delivered the controlling signal for low speed hightorque forward rotation of the motor M, it detects at step #17-5 whetheror not the auto flag AUTOF is "1", and when the flag AUTOF is "1", themicrocomputer μC waits for the predetermined time I₁ at step #17-6 andthen delivers, at step #17-7, a signal for changing over the motor M tohigh speed low torque forward rotation. On the contrary, when the flagAUTOF is not "1" at step #17-5, the motor M is continuously driven torotate in the low speed high torque condition. In either case, themicrocomputer μC then waits at step #17-8 until the switch S₆ indicatingcompletion of the winding of the film by one frame is turned off. Thus,after turning off of the switch S₆, the microcomputer μC controls atstep #17-9 to stop rotation of the motor M whereafter the programreturns to the original routine of FIG. 24.

Now, a subroutine illustrating detailed operation of the motor stoppingstep #17-9 of FIG. 30 will be described with reference to a flow chartof FIG. 32. At first at step 1, the microcomputer μC delivers a motorstopping signal, and then waits at step 2 for an interval of timesufficient for the motor M to stop its rotation completely. After then,the microcomputer μC delivers a signal for deenergizing the motor M (asignal for turning on all the transistors Tr₄ to Tr₉ of the motordriving circuit MD). Subsequently, the microcomputer μC stops the timerI at step 4 and then inhibits timer interrupt at step 5 whereafter theprogram returns to the subroutine of FIG. 30 and then to the routine ofFIG. 24.

Referring back to FIG. 24 again, after completion of the film windingoperation, the program returns to step #7 so that a similar sequence ofoperations will be repeated.

Now, description will be given of the timer interrupt which is providedto perform rewinding of a film when photographing of a photographablenumber of frames of a film is completed and the film cannot be wound anymore during such a film winding operation as described above. Asdescribed hereinabove, when a predetermined time (for example, 1.5seconds) elapses from starting of the timer I upon starting of thewinding operation, the microcomputer μC executes a timer interruptroutine illustrated in FIG. 33 in order to perform a film rewindingoperation. In the routine of FIG. 33, at first at step #100, themicrocomputer μC inhibits interruption at the interrupt terminals INT₁,INT₂ thereof, and then at #102, the motor stopping subroutineillustrated in FIG. 32 is executed. Since the motor stopping subroutinehas been described hereinabove, description thereof is omitted here toavoid redundancy.

Subsequently at step #102, the microcomputer μC waits until therewinding switch S₇ is turned on, and upon turning of the rewindingswitch S₇, the microcomputer μC determines at step #103 whether or notthe switch S₄ for compulsorily changing over the motor M to a low speedhigh torque rotation condition is on. Thus, when the switch S₄ is on andhence the low speed high torque driving mode is selected, the auto flagAUTOF indicating the automatic change-over mode is reset to "0" at step#104. To the contrary, when the switch S₄ is not on, the programadvances to step #105 at which a battery checking subroutine fordetermining whether the voltage of the power source battery issufficiently high to allow automatic change-over of the motor drivingmode is executed. In either case, the microcomputer μC controls, at step#106, the motor M to rewind a film in accordance with the selected speedcontrol of the motor.

A subroutine for the motor control is illustrated in a flow chart ofFIG. 34. Referring to FIG. 34, at first at step #200, the microcomputerμC delivers a signal instructing low speed high torque reverse rotationof the motor M, and then at step #201, it is determined whether or notthe auto flag AUTOF is in the set ("1") state. Here, if the auto flagAUTOF is not in the set state, the program advances to step #204, but onthe contrary if the flag AUTOF is in the set state, the program advancesto step #202 at which the microcomputer μC waits for the predeterminedinterval of time I₁ and then to step #203 at which the driving of themotor M is changed over to high speed low torque reverse rotation,whereafter the program advances to step #204. At step #204, the filmdetecting switch S₅ is checked to determine whether or not the film hasbeen completely taken into the film cartridge to complete the rewindingoperation. Thus, in case the film has not completely been taken into thecartridge, the microcomputer μC waits for completion of the rewindingoperation. Thus, when it is determined at step #204 that the film hasbeen completely taken into the cartridge, the microcomputer μC controlsat step #205 to stop rotation of the motor M and then returns theprogram to step #7 of the routine of FIG. 24.

Subsequently, control of the motor M upon initial winding of a film whenthe film is mounted in position in the camera will be described. It isto be noted however that since a film is wound by a plurality of, 3 inthe following description, frames for initial winding thereof, it isadvantageous to determine, just before completion of each winding of thefilm by one frame, whether or not the film should be wound continuouslythereafter. To this end, a switch may be provided which is turned ondirectly before completion of winding of a film by one frame. Such aswitch may be located, for example, for operation by the windingstopping cam 24 shown in FIG. 21. While such a switch may beadditionally provided, the following description proceeds under anassumption that the rewinding switch S₇ of the circuit of FIG. 23 isomitted and such a switch S₇ is inserted instead that is turned ondirectly before completion of winding of a film by one frame.

When a rear cover not shown of the camera is closed, the switch S₃ isturned on. Thereupon, the microcomputer μC receives at the interruptterminal INT₂ thereof a signal which changes from an "H" level to an "L"level and thus executes an interrupt routine "INT₂ " a flow chart ofwhich is illustrated in FIG. 35. In the interrupt routine INT₂, themicrocomputer μC inhibits, at first at step #300, execution of theinterrupt routine "INT₁ " by turning on of the photographing preparingswitch S₁. Subsequently, a variable N is initially reset to "0" at stop#301 and then the power supply transistor Tr₁ is turned on at step #302.Then at step #303, it is detected whether or not the mode in which themotor M is compulsorily driven to rotate at a low speed is selected, andwhen it is detected that the low speed mode is selected, or when it isdetected at subsequent step π305 that no film is mounted in the camera,the auto flag AUTOF indicating the automatic change-over mode is resetto "0" at step #304. On the other hand, when it is determined at step#303 that the low speed mode is selected and then it is determined atstep #305 that a film is mounted in position in the camera, the batteryis checked at step #306 to selectively determine a driving speed of themotor M. After the step #304 or step #306, the program advances to step#307 at which the motor M is controlled for initial winding at the film.

A subroutine of controlling the motor M for initial winding of a film isillustrated in a flow chart of FIG. 36. Referring to FIG. 36, themicrocomputer μC controls at first at step #400 for low speed hightorque forward rotation of the motor M, and then determines at step #401whether or not the auto flag AUTOF indicating the automatic change-overmode is in the set state. Here, when the auto flag AUTOF is not in theset state, the program skips to step #404, but on the contrary when theauto flag AUTOF is in the set state, the microcomputer μC waits for apredetermined interval of time at #402 and then controls at step #403 tochange over the driving of the motor M to high speed low torque forwardrotation.

After then, the program advances to step #404 at which the microcomputerμC waits until the switch S₇ which is arranged to be turned on directlybefore completion of a film winding operation by one frame. Thus, whenthe switch S₇ is turned on, the microcomputer μC controls the motor Mfor low speed high torque forward rotation at step #405. Then at step#406, the microcomputer μC waits until the winding completion switch S₆is turned off, and after turning off of the switch S₆, the variable N isincremented by one at step #407, and then at step #408, it is determinedwhether or not the variable N is equal to 3. If the variable N is notequal to 3 here at step #408, then it is determined at step #409 whetheror not the auto flag AUTOF is in the set state, and if the auto flagAUTOF is in the set state, the program advances to step #403 in order todrive the motor in the forward direction in a high speed low torquecondition to wind the film On the contrary when it is determined at #409that the auto flag AUTOF is not in the set ("1") state, the programadvances to step #404 in order to perform winding of the film by lowspeed high torque rotation of the motor. Thus, when it is determinedfinally at step #408 that the variable N is equal to 3 and accordinglythe film has been wound up by three frames, the motor M is stopped atstep #410 in order to terminate the initial winding operation,whereafter the program returns to step #7 of FIG. 24.

It is to be noted that where the rewinding switch is replaced by theswitch which is turned on directly before completion of winding of afilm by one frame, the timer interrupt routine of FIG. 33 must bemodified. In particular, the step #102 at which the microcomputer μCwaits until the rewinding switch S₇ must be omitted. Accordingly, afterstopping of the motor M at step #101, the program advances directly tostep #103.

Various possible modifications of the electric circuits of the camerashown in FIGS. 20 to 32 will be described below.

FIG. 37 shows a modification to the winding subroutine of the flow chartof FIG. 30 where the rewinding switch S₇ is replaced by the switch S₇which is turned on directly before completion of winding of a film byone frame. In the winding subroutine of FIG. 37, two steps #17-7a and#17-7b are added after step #17-7. In particular, the microcomputer μCwaits at step #17-7a until the switch S₇ is turned on. After then, themicrocomputer μC changes over the motor M to low speed high torqueforward rotation at step #17-7b.

The two steps are provided by the following reason. In the film windingand rewinding mechanism shown in FIG. 21, the winding stopping cam 24 isstopped positively after one complete rotation thereof by the windingstopping lever 22. Accordingly, the torque will increase when suchwinding of the film by one frame is completed. Consequently, when themotor M is rotating at a high speed with a low torque, the motor M maynot provide a force sufficient to continue the rotation thereof.Therefore, the motor M is changed over, at steps #17-71 and #17-7b, tothe low speed high torque rotation just before completion of winding ofthe film by one frame in order to assure rotating of the motor M.

Meanwhile, in the embodiment shown in FIGS. 24 to 36, in case it isdetermined that the rotational speed of the motor M can be changed overupon initial winding of a film similarly as in normal winding of thefilm by one frame, it is changed over to high speed rotation after lapseof the predetermined interval of time after starting of low speedrotation. This is because when the film is to be wrapped around thespool 48 upon initial winding of the film, the low speed high torquerotation of the motor M will allow the film to be wrapped around thespool more readily than the high speed low torque rotation.

Accordingly, a following modification may be recommended. In particular,a switch for detecting that a film has been wrapped around a spool(hereinafter referred to as SLS switch) is provided such that when theSLS switch is on (the film is not yet wrapped around the spool), themotor M may be rotated in a low speed high torque condition, and whenthe SLS switch is turned off (when the film is wrapped around thespool), the motor may be changed over to high speed low torque rotation.Here, the SLS switch may be constituted from a conductive pressingmember which is projected from the camera body for contacting with thespool which is in turn formed, for example, from conductive rubber suchthat when a film is wrapped around the spool, electric connectionbetween the conductive spool and the conductive pressing member isinterrupted by the film thereby to turn the switch off.

In order to match operation of the microcomputer μC with the modifiedarrangement, the subroutine of the flow chart of FIG. 35 itself need notbe modified but the subroutine of the flow chart of FIG. 36 should bemodified, for example, to such as shown in a flow chart of FIG. 38. Inparticular, the step of #402 of FIG. 36 at which the microcomputer μCwaits for the predetermined interval of time is replaced by a modifiedstep #402' of FIG. 38 at which it is determined whether or not the SLSswitch is on and, when the SLS switch is on, the microcomputer μC waitsuntil the SLS switch is turned off whereupon the program advances tostep #403 in order to drive the motor M to rotate in a high speed lowtorque condition. In this instance, the SLS switch and an input terminalof the microcomputer μC for receiving a signal from the SLS switch mustbe added to the block diagram of FIG. 19.

By the way, if it is assumed that initial winding and rewindingoperations of a film have no direct relation with photographing, theyneed not be performed particularly at a high speed. if such operationsare performed at a far lower speed, then following advantages will beforecast.

(a) Electric current is reduced.

(b) Noise production is reduced comparing with that in high speedrotation.

In order to mach operation of the microcomputer μC with the low speedhigh torque rotation of the motor, the pertinent motor controllingroutines must only be modified such that any step having to do withchange-over of the motor driving mode or with high speed rotation of themotor is omitted. Accordingly, detailed description is omitted herein.

Further, in the construction shown in FIGS. 24 to 36, change-over of thedriving speed of the motor M from the low speed high torque rotation tothe high speed low torque rotation and change-over from the high speedlow torque to the low speed high torque rotation are performed uponlapse of a predetermined time. However, according to the construction,there is no parameter in connection with the capacity of the powersource battery. Accordingly, an optimum timing at which the speed is tobe changed over with respect to the capacity of a given battery cannotbe determined for the given battery. Therefore, in a following modifiedform described below, change-over from the low speed high torquerotation to the high speed low torque rotation is performed in responseto a voltage of the battery which is monitored after starting of lowspeed high torque rotation of the motor M. However, in the followingmodification, the driving speed of the motor M is once changed over tothe high speed low torque rotation and then to the low speed high torquerotation because, in following cases, the winding efficiency is low, andhence, for example, much time is required for winding.

(a) When the voltage at an instant at which the motor M is changed overto the high speed low torque rotation is lower than a predeterminedlevel.

(b) When the voltage at an instant at which the motor M is changed overto the high speed low torque rotation is higher than a predeterminedvoltage V₂ but is not restored to another predetermined voltage V₁within a predetermined time (although this may not be necessarydepending upon a level of the voltage V₂). Here, V₁ >₂. Further, sincehigh speed low torque rotation of the motor M by a battery of a lowcapacity will make the efficiency low when the load increases suddenly,the degree of dropping of the voltage of the power source is monitoredalso in this case in order to change over the motor M from the highspeed low torque rotation to the low speed high torque rotation.

This is described more in detail with reference to FIG. 39 wherein theaxis of abscissa indicates the time when a film is wound and the axis ofordinate indicates the voltage with the capacity of the battery taken asa parameter. It is assumed that capacities of batteries indicated bycurves A, B, C, D in FIG. 34 have a relationship A>B>C>D. Now, if it isintended to make the actual torque of the motor M have a magnitude at anoptimum point at which the motor M is to be changed over from the lowspeed high torque rotation to the high speed low torque rotation, it isknown that the time until the required torque is reached variesdepending upon the capacity of the battery (current flow which can bederived from the battery). Conversely, if the capacity of the battery isknown, then the time required until the necessary torque is reached canbe found. Then, the capacity of the battery can be found by detecting atime until a predetermined voltage is restored after the motor M isengagized, and by changing the predetermined voltage, the restorationtime in accordance with a capacity of each battery can be changed.Accordingly, if the predetermined voltage is determined for therespective capacity of each battery such that the time until thepredetermined voltage is restored and the time until the necessarytorque is reached may coincide with each other, then an optimum pointfor change-over of the speed can be obtained for a change of thecapacity of the battery. However, since the individual predeterminedvoltages will vary more or less by the capacities of the batteries, ifan average of them is calculated to determine a single predeterminedvoltage, then a speed change-over point which is optimum for most casescan be obtained. In FIG. 39, such a predetermined voltage is representedat V₁, and thus it can be seen that the change-over time varies for eachof batteries of various capacities (indicating that the necessary torqueis substantially constant). When the driving speed of the motor M ischanged over from the low speed high torque condition to the high speedlow torque condition, a battery having a low capacity such as shown bythe curve D of FIG. 39 will exhibit a lower voltage than the voltagelevel V₂ so that the torque produced by the motor will be too low.Consequently, a longer time will be required than when the driving speedof the motor is not changed over. Accordingly, in this case, the drivingspeed of the motor is changed over from the high speed low torquerotation to the low speed high torque rotation.

On the other hand, also in the case of a battery as indicated by a curveC of FIG. 39, that is, in the case of a battery the voltage of which isnot restored to a predetermined voltage within a predetermined timeafter the driving speed of the motor has been changed over, because alonger tim is required than when the motor driving speed is not changedover, the driving speed of the motor is changed over from the high speedlow torque rotation to the low speed high torque rotation after lapse ofthe predetermined time. Further, in case the load increases suddenly asdescribed above, for example, in case the load increases suddenly afterthe winding stopping mechanism has been rendered operative, where abattery having such a capacity that does not provide the required torqueduring high speed low torque rotation of the motor is used, the motormust necessarily be changed over to the low speed high torque rotationin order to obtain a high torque. In the present modification, this isdetected by dropping of the voltage of the battery. Accordingly, theswitch S₅ which is turned on directly before completion of winding of afilm by one frame can be omitted. Further, since the voltage of thebattery is normally detected upon winding of a film, no battery checkingcircuit is required in the following modification. Part of an exemplaryelectric circuit necessary to attain this is shown in FIG. 41.

Referring to FIG. 40, comparators COMP₅, COMP₆, COMP₇ are connected tocompare a divided voltage of a voltage of the power source withrespective reference voltages V'₁, V'₃, V'₂ (corresponding to V₁, V₃, V₂of FIG. 39, respectively) and each provide an "L" level when thereference voltage is higher than the divided voltage. A D-type flip-flopDFF latches an output of the comparator COMP₇ in response to a latchingsignal from the microcomputer μC. It is to be noted that themicrocomputer μC has additional terminals for receiving signals from thecomparators COMP₅, COMP₆ and the D-type flip-flop DFF and an additionaloutput terminal for delivering a latching signal to the D-type flip-flopDFF.

A modification to the winding subroutine of FIG. 30 or to that of FIG.37 for controlling a film winding operation where the modified circuitof FIG. 40 is employed is shown in FIG. 41. Referring to FIG. 41, atfirst at step #500, the microcomputer μC enables timer interrupt, andthen at step #501, resets and re-starts a time. Subsequently at step#502, the microcomputer μC detects a state of an auto flag AUTOFindicating the automatic change-over mode of the motor driving speed,and then when the flag is not in the set state, the program advances tostep #512 at which the motor is controlled to rotate in the forwarddirection in a low speed high torque condition and then waits at step#513 until the winding of the film is completed.

On the contrary, when the flat AUTOF is in the set state at step #502,the program advances to step #503 at which the motor M is controlled torotate in the forward direction in a low speed high torque condition.Then at step #504, output of the comparator COMP₅ is checked todetermine whether or not the power source voltage is higher than thepredetermined voltage V₁, and when the determination is affirmative, theprogram advances to step #502. To the contrary, when the power sourcevoltage is not higher than the predetermined voltage V₁, the programadvances to step #505 at which the microcomputer μC determines whetheror not winding of the film is completed, and in case the film winding isnot yet completed, the program returns to step #504. On the other hand,in case of completion of the film winding at step #505, the programadvances to step #514 at which a motor stopping subroutine is executedto stop the motor M.

At step #506, the motor M is changed over to the high speed low torqueforward rotation, and then at step #507, a latching signal is deliveredto the D-type flip-flop DFF in order to cause the latter to latch asignal which indicates whether the current power source voltage is lowerthan the predetermined voltage V₂ shown in FIG. 39 or not. Subsequentlyat step #508, output of the D-type flip-flop DFF is received in order tocheck whether or not the output signal is at the "H" level, and if it isat the "L" level, then the program advances to step #512 at which themotor is changed over again to the low speed high torque rotation inorder to improve the efficiency of the motor. To the contrary, when thelatched signal is at the "H" level at step #508, the program advances tostep #509 at which the microcomputer μC checks output of the comparatorCOMP₅ in order to determine whether or not the power source voltage hasbecome higher than the reference voltage V₁ within the predeterminedtime I₂ shown in FIG. 39 lapse of which is checked at step #511, and incase the determination is negative, the microcomputer μC determines thatthe capacity of the battery is too low for high speed low torquerotation of the motor M and thus advances, passing steps #510 and #511,to step #512 in order to change over the motor M to the low speed hightorque forward rotation.

On the other hand, when it is determined at step #509 that the powersource voltage has become higher than the reference voltage V₁ withinthe fixed time I₂, the program advances to step #515 at which it isdetermined whether or not the power source voltage is now higher thanthe reference voltage V₃, and if the former is higher than the latter,the program advances to step #516 at which a film winding operation isperformed until completion of the winding. Upon completion of thewinding operation, the program advances to step #514 at which the motorstopping subroutine is performed in order to stop the motor. On thecontrary, in case the load has been increased by the winding stoppingmechanism before completion of the winding of the film so that the powersource voltage is lower than the reference voltage V₃, the programadvances from step #515 to step #512 in order to change over the motor Mto the low speed high torque forward rotation. Then at step #513, themicrocomputer μC waits until the winding of the film is completed, andupon completion of the film winding, it controls the motor M to stop atstep #512, whereafter the program returns to the original routine. It isto be noted that while in the present modification the reference voltagewhen the motor is changed over from the low speed high torque rotationto the high speed low torque rotation and the reference voltage when itis to be determined whether change-over to the high speed low torquerotation is suitable for not are equal to the same voltage V₁, they maybe different voltages if necessary.

A following modification is made to the modification of FIGS. 40 and 41and is only different from the latter in that when it is to bedetermined whether another reverse change-over to the low speed hightorque rotation after change-over from the low speed high torquerotation to the high speed low torque rotation is necessary or not, thepower source voltage is not detected normally but otherwise it isdetected only after lapse of a predetermined time after change-over tothe high speed low torque rotation in order to check the power sourcevoltage only at the point of time. An electric circuit constructed toattain this shown in FIG. 42. Comparison of the circuit shown in FIG. 42with the circuit shown in FIG. 40 will reveal that they are similar inconstruction except that the comparator COMP₇ and the D-type flip-flopDFF of the latter are omitted in the former. A modified flow chart ofoperation of the microcomputer μC for controlling the circuit of FIG. 42is shown in FIG. 43. In the flow chart of FIG. 43, the steps #507 and#508 of the flow chart of FIG. 41 are replaced respectively by a step#507' at which a predetermined time I₂ is counted and a step #508' atwhich it is checked whether or not output of the comparator COMP₅ is atthe "H" level such that when output of the comparator COMP₅ is at the"H" level, the program may advance to step #515 but on the contrary whenoutput of the comparator COMP₅ is at the "L" level, the program mayadvance to step #512. Meanwhile, the steps #509 to #511 of FIG. 41 areomitted. The remaining steps of operation are same as those of the flowchart of FIG. 41.

It is to be noted that while the two modifications shown in FIGS. 40 to43 make use of change-over of the driving speed of the motor only forwinding of a film, they may naturally be used for initial winding orrewinding of a film.

A following embodiment of motor controlling system of the presentinvention is constituted such that the rotational frequency or speed ofa motor is monitored so that when an optimum rotational frequency forintended changeover of the speed of the motor is detected, the motor ischanged over from a low speed high torque rotational condition to a highspeed low torque rotational condition or vice versa. Such detection ofthe optimum rotational frequency to change over the driving speed of themotor is advantageous in that it will substantially normally assureefficient change-over of the speed of the motor because the cross pointbetween the straight lines (T-N)α, (T-N)β in FIG. 2 is experimentallysubstantially constant with respect to the rotational frequency or speedof the motor even if the capacity of a battery varies.

In the embodiment shown in FIG. 44, an encoder disk 80 is mounted on amotor shaft 26 of such a motor M as shown in FIG. 21 which is used forwinding and rewinding of a film, and a reflective photocoupler 82 islocated in an opposing relationship to the encoder disk 80. A pattern ofalternate reflecting portions 80a and non-reflecting portions 80b isformed on the encoder disk 80, and the photocoupler 82 convertsreflected light from the pattern of the seconder disk 80 into anelectric signal which is transmitted to a microcomputer μC in order tomonitor the rotational frequency of the motor M.

An electric circuit of the motor controlling system of the embodiment ofFIG. 44 is shown in FIG. 45. Referring to FIG. 45, the circuit shown isonly different from the circuit of FIG. 23 in that the battery checkingcircuit BC of the latter is replaced by a photocoupler circuit PCL.However, the program of the microcomputer μC is modified such that apredetermined interrupt routine is executed in response to a signal whenthe photocoupler PCL receives light reflected from any of the reflectingportions 80a of the pattern of the encoder disk 80. As to flow chartsindicating operation of the microcomputer μC, those of the windingsubroutine shown in FIG. 30 and the motor control II subroutine forrewinding shown in FIG. 34 are modified and the interrupt routinementioned above is additionally provided. Further, the step #16 of FIG.24 is omitted and a step for setting an auto flag AUTOF is inserted inplace.

A modified winding subroutine is shown in FIG. 46. Referring to FIG. 46,the microcomputer μC first inhibits interruption at an interruptterminal INT₁ thereof at step S17-1, and then enables, at step S17-2,timer interrupt for detecting a taut condition of a film. Subsequentlyat step S17-3, the timer I is reset and started, and then at step S17-4,the microcomputer μC delivers data for controlling the motor to rotatein the forward direction at a low speed with a high torque. The stepsmentioned just above are quite same as the steps #17-1 to #17-4 of FIG.30.

Subsequently at step S17-5, the microcomputer μC determines whether theauto flag AUTOF for automatically changing over the rotational frequencyof the motor is in the set state or not, and where it is in the setstate, a flag FISF for ignoring reading of a timer II for the first timewhen the rotational frequency of the motor is to be detected is set atstep S17-6, and then a signal for turning on a light emitting diode LEDof the photocoupler circuit PCL is delivered to the photocoupler circuitPCL at step S17-7. Upon reception of the signal, the photocouplercircuit PCL causes the light emitting diode LED of the photocoupler tobe lit. The microcomputer μC then enables counter interrupt at stepS17-8.

Here, when light emitted from the light emitting diode LED and reflectedfrom a reflecting portion 80a of the encoder disk 80 is received by alight receiving element of photocoupler, the photocoupler circuit PCLdelivers to the microcomputer μC a signal which changes from an "H"level to an "L" level. Upon reception of such a signal changing from the"H" level to the "L" level from the photocoupler circuit PCL, thecounter interrupt which will be hereinafter described occurs at themicrocomputer μC to detect the rotational frequency of the motor M. Thephotocoupler circuit PCL produces a signal of the "H" level if theamount of incident light to the light receiving element decreases belowa predetermined level. Accordingly, each time a point on the encoderdisk 80 at which it receives light emitted from the light emitting diodeof the photocoupler moves from a non-reflecting portion 80b to areflecting portion 80a of the encoder disk 80, the counter interruptroutine is executed in order to detect the rotational frequency(rotational speed) of the motor M.

Subsequently, the microcomputer μC waits at step S17-9 until winding ofthe film by one frame is completed whereupon the switch S₆ is turnedoff. It is to be noted that where the auto flag AUTOF for automaticallychanging over the rotational speed of the motor M is not in the setstate at step S17-5, the steps S17-6 to S17-8 are skipped andaccordingly the program advances directly to step S17-9.

When completion of the winding of the film is detected at step S17-9,the program advances to step S17-10 at which the timer II is stopped,and then to step S17-11 at which counter interrupt is inhibited. Then atstep S17-12, the light emitting diode LED of the photocoupler circuitPCL is turned off, and then at step S17-13, the motor stoppingsubroutine as illustrated in FIG. 32 is executed, whereafter the programreturns to the initial routine from which the initial subroutine of FIG.46 is entered.

NOW, the counter interrupt routine which is entered in response to asignal from the photocoupler circuit PCL will be described withreference to a flow chart of FIG. 47. Here, detection of the rotationalfrequency of the motor M in the present embodiment is effected byreading a time required for rotation of the motor M by a predeterminedangle.

At first at step #600, the microcomputer μC executes a timer readingsubroutine which is illustrated in FIG. 48. Referring to FIG. 48, themicrocomputer μC determines at first at step #600-1 whether or not theflag FISF for ignoring reading of the timer for the first time is in theset state, and if the flag FISF is in the set state, a predeterminedvalue TA is set to a timer register T2 at step #600-2. Here, TA >TK1,and accordingly the rotational frequency of the motor M is inhibitedfrom being changed over from a low speed high torque rotationalcondition to a high speed low torque rotational condition. This isbecause, due to the fact that the initial position of the encoder disk80 relative to the photocoupler 82 is not fixed and cannot be foreseen,the angle (distance) over which the motor M has rotated by a point oftime at which the timer is read for the first time is not, in mostcases, equal to one complete cycle of rotation of the motor andaccordingly, if a rotational frequency of the motor is calculated from avalue thus read for the first time from the timer, perhaps it will bedifferent from an actual rotational speed of the motor M. Therefore, thestep #600-2 is provided in order to prevent the motor M from beingchanged over in error from the high speed low torque rotationalconditions to the low speed high torque rotational condition in responseto a detected rotational speed where the detected rotational speed maypossibly be different from an actual rotational speed. Then at step#600-3, the flag FISF is reset to "0" and then the program returns tothe initial routine of FIG. 47. On the other hand, in case the flag FISFis not in the set state at step #600-1, the program advances to step#600-4 at which a counted value of the timer II operation of which wasstarted upon the preceding execution of the counter interrupt routine isstored into the timer register T2, whereafter the program returns to theinitial routine of FIG. 47.

Referring back to FIG. 47, after return from the subroutine of FIG. 48,the timer II for detecting a rotational speed of the motor M is resetand started at step #601, and then at step #602, the microcomputer μCdetermines whether a flag HiF for controlling the motor M to rotate in ahigh speed low torque rotational condition is in the set state or not.Here, if the flag HiF is not in the set state, that is, if the motor isrotating in a low speed high torque rotational condition, then theprogram advances to step #603 at which it is determined whether or notthe interval of time T2 which was read at step #600-4 of FIG. 48 andafter lapse of which subsequent counter interrupt is to occur is equalto or smaller than the predetermined time TK1.

Here, in case the read time T2 is equal to or smaller than thepredetermined time TK1, the microcomputer μC determines that the actualrotational speed of the motor is higher than a predetermined level (arotational speed corresponding to a rotational frequency at a crosspoint between the straight lines (T-N)α and (T-N)β shown in FIG. 2) andthus changes over the controlling condition of the motor M to the highspeed low torque rotational condition More in detail, at first at step#604, the flag HiF indicating the high speed low torque rotationalcondition is set to "1". Then, in order to determine the rotationaldirection of the motor M, it is determined at step #605 whether or not arewinding flag REWF indicating a film rewinding condition is in the setstate, and where the rewinding flag REWF is in the set state, theprogram advances to step #606 at which the motor M is caused to rotateat a high speed in the reverse direction, but on the contrary where therewinding flag REWF is not in the set state, the program advancesotherwise to step #607 at which the motor M is controlled to rotate at ahigh speed in the forward direction. After the step #606 or #607, theprogram returns to the original routine from which the counter interruptroutine was entered.

Meanwhile, where the time T2 read at step #600-4 of FIG. 48 is greaterthan the predetermined time TK1 at step #603, the program returns to thesame original routine without changing over the speed of the motor Mbecause operation at a higher speed can be attained if the rotationalspeed of the motor M is not changed over.

On the other hand, where the flag HiF is already in the set state atstep #602 and accordingly the motor M is already in the high speed lowtorque rotational condition, the program advances to step #608 at whichit is determined whether or not the read time T2 is equal to or smallerthan the predetermined time TK1. Then, if the read time T2 is equal toor smaller than the predetermined time TK1, then the program returns tothe original routine without changing over the speed of the motor Mbecause operation at a higher speed can be attained if the rotationalspeed of the motor M is not changed over.

On the contrary, if the read time T2 is greater than the predeterminedtime TK1 at step #608, the motor M is changed over to the low speed hightorque rotational condition because operation at a higher speed can beattained by the low speed high torque rotation of the motor M Thus, atstep #609, it is determined whether or not the rewinding flag REWF is inthe set ("1") state, and if the flag REWF is in the set state, then themotor M is controlled at step #610 to rotate in the reverse direction ina low speed high torque condition in order to wind the film, but on thecontrary if the flag REWF is not in the set state at step #609, theprogram advances to step #611 at which the motor M is rotated in theforward direction in a low speed high torque condition, whereafter theprogram returns to the original routine.

Now, operation of the microcomputer μC when a film is to be rewound willbe described with reference to a flow chart of FIG. 49.

When a predetermined value is reached by a counted value of a timer Iwhich is counting the time during winding of a film, the microcomputerμC executes a timer interrupt subroutine illustrated in FIG. 49. Afterthe subroutine of FIG. 49 is entered, the microcomputer μC firstinhibits, at step #700, interrupt at the interrupt terminal INT₁ thereofand counter interrupt, and then at step #701, the timer II for suchcounter interrupt is stopped. Then at step #702, the microcomputer μCexecutes the motor stopping subroutine shown in FIG. 32, and then waits,at step #703, until the switch S₇ which is turned on in order to startrewinding of a film is turned on. Thus, upon turning on of the switch S₇after completion of winding of the film, the microcomputer μC determinesat step #704 whether or not the low speed high torque rotationalcondition is selected, and where it is already selected, the auto flagAUTOF is reset to "0" at step #705, but on the contrary where the lowspeed high torque rotational condition is not selected, the auto flagAUTOF is set to "1" at step #706. In either case the program thenadvances to step #707 at which the microcomputer μC delivers to themotor controlling circuit MC a control signal for rotating the motor Min the reverse direction (in the direction to rewind the film) in thelow speed high torque condition.

Subsequently at step #708, the microcomputer μC determines whether ornot the auto flag AUTOF is in the set ("1") state, and if it is not inthe set state, the program jumps to step #713. To the contrary, if theauto flag AUTOF is in the set ("1") state, the program advances to step#709 at which the flag FISF for ignoring reading of the timer for thefirst time is set to "1", and then the rewinding flag REWF is set to "1"at step #710. Then at step #711, the microcomputer μC delivers a signalfor turning on the light emitting diode LED of the photocoupler circuitPCL in order to cause the light emitting diode LED to emit light,whereafter the microcomputer μC enables counter interrupt at step #712.

Then at step #713, the microcomputer μC waits until the film rewindingoperation is completed so that the film is entirely taken up into a filmcartridge, whereafter the program advances to step #714 at which therewinding flag REWF is reset to "0" and to step #715 at which countingof the timer II is stopped. Subsequently, the microcomputer μC inhibitscounter interrupt at step #716, and then at step #717, delivers a signalfor turning off the light emitting diode LED of the photocoupler circuitPCL to extinguish the same. Then at step #718, the microcomputer μCexecutes the motor stopping subroutine shown in FIG. 32, whereafter theprogram returns to step #7 of FIG. 24.

While here in the present modification the encoder disk and thephotocoupler of the reflective type are used to detect the rotationalspeed of the motor M, they may be replaced by a pattern member having aconductive coded pattern thereon and a switch having a contact orcontacts for slidably contacting with the coded pattern of the patternmember, respectively.

An arrangement of a modified form of the construction just described isshown in FIG. 50. Referring to FIG. 50, a pattern disk 84 is securelymounted on a motor shaft 26 of a motor M and has two concentricalseparate conductive patterns each having conductive portions 84a andnon-conductive portions 84b arranged in an alternate relationshiptherein. A pair of contacts 86 are mounted for slidably contacting withthe individual coded patterns on the pattern disk 84. An equivalentcircuit of the detecting device having such a construction as describedabove for detecting the rotational frequency of the motor is illustratedin FIG. 51. As will be appreciated from FIG. 51, the microcomputer μCreceives at an input terminal IP₆ thereof a signal changing from an "H"level to an "L" level each time the contacts 86 are brought into contactwith any of the conductive portions 84a of the coded patterns on thepattern disk 84. Accordingly, the microcomputer μC may use such a signalin place of a signal from the photocoupler circuit PCL.

Thus, where the rotational speed of the motor M is detected tosuccessively and automatically change over the motor M between the highspeed low torque rotational condition and the low speed high torquerotational condition in this manner, high speed operation is assuredeven if the torque of the motor M fluctuates while winding or rewindingof a film or energizing of the shutter is to be performed, and even ifthe capacity of the power source battery decreases, the number of timesat which winding or rewinding of a film or energizing of the shutter canbe performed can be increased by selection of the low speed high torquerotational condition in which power consumption is low.

FIGS. 52 to 57 show a further embodiment of motor controlling system ofthe present invention wherein it is applied to a film winding andrewinding mechanism of a camera. In the present embodiment, a body of amotor which is used for winding of a film is located within a chamber ofa spool such that a motor cylinder is rotated together with the spool.FIG. 52 is a perspective view of the film winding and rewindingmechanism, FIG. 53 is a transverse sectional view of the spool andcorresponds to a transverse sectional view taken along line Q--Q of FIG.55, FIG. 54 is a bottom plan view of the spool of FIG. 53, FIG. 55 apartial longitudinal sectional view taken along line E-P-E of FIG. 53,FIG. 56 a partial longitudinal sectional view taken along line F-P-F ofFIG. 53, and FIG. 57 a partial fragmentary perspective view of the spoolof FIG. 53 as viewed from the bottom side.

Referring to FIG. 52, a spool 48 is formed as an integral member with anouter cylinder of the motor M and has a conductive pattern 88 formed ona bottom face thereof. Three contacts 86a, 86b, 86c are located in aconcentrical relationship around a motor shaft 26 on a stationary memberfor slidably contacting with the conductive pattern 88 on the spool 48.

As shown in FIG. 52, an electric base plate 90 is mounted on a holder 92which forms a lower wall of the motor M, and three concentricalconductive coded patterns 88a, 88b, 88c are formed on a lower face ofthe electric base plate 90. The three contacts 86a, 86b, 86c are locatedparticularly for slidably contacting with the conductive coded patterns88a, 88b, 88c, respectively. Thus, power is supplied to the motor viathe conductive coded patterns 88a, 88b, 88c. As seen from the bottomplan view of the electric base plate 90 and hence of the spool 48 ofFIG. 54, through-holes 88a, 88b₁, 88c₁ are formed through the conductivecoded patterns 88a, 88b, 88c, respectively. Meanwhile, as seen from FIG.57, three perforations 92a, 92b, 92c are formed in the holder 92, andmetal shafts 94a, 94b, 94c are fitted in the perforations 92a, 92b, 92c,respectively.

The conductive coded patterns 88a, 88b, 88c and conductive codedpatterns 96a, 96b, 96c (only the conductive coded pattern 96c is shownin FIG. 55) formed on a reverse face of the electric base plate 90 areelectrically connected to each other via the through-holes 88a₁ 88b₁88c₁ of the conductive coded patterns 88a, 88b, 88c, respectively. Asshown in FIGS. 55 and 56, head portions of the metal shafts 94a, 94b,94c are soldered to the conductive coded patterns 96a, 96b, 96c on thereverse face of the electric base plate 90. Accordingly, power suppliedfrom the contacts 86a, 86b, 86c is transmitted to the metal shafts 94a,94b, 94c, respectively.

A commutator 98 of the motor M includes integrally rotatable portions98a and 98b. A pair of brushes 100a, 100b are secured to the holder 92for contacting with the portions 98a, 98b of the rotating commutator 98,respectively. Each of the brushes 100a, 100b has a contact 100a₁ or100b₁ for engagement with the portion 98a of the commutator 98 andanother contact 100a₂ or 100b₂ for engagement with the lower portion 98bof the commutator 98, respectively. Further, foot portions of the metalshafts 94a, 94b are soldered to the brush 100a while the remaining metalshaft 94c is soldered to the brush 100b. Accordingly, power is suppliedto the commutator 98 of the motor M via the brushes 100a, 100b.

It is to be noted that the motor may otherwise be of a different typewherein a brush and a commutator or arranged at axially oppositepositions of the motor. In such a case, two electric base plates eachhaving double concentrical patterns thereon may be arranged at suchaxially opposite positions of the motor.

Further, while in the embodiment described just above the brushes 100b₁,100b₂ corresponding to a center tap are formed in an integralrelationship, they may otherwise be formed as separate members whilequadruple concentrical patterns may be provided on the base plate.

It will be appreciated here that the motor controlling systems of thefirst to third embodiments and possible modifications and variations ofthe same described above can be applied in any combination to the dcmotors of the first to seventh embodiments and possible variations andmodifications of the same described above.

FIGS. 58 to 61 show a still further embodiment of motor controllingsystem of the present invention. FIG. 58 is a longitudinal sectionalview of a dc motor in which a motor controlling system of the inventionis incorporated, FIGS. 59 and 60 are transverse sectional views showinga centrifugal switch in different positions, and FIG. 61 is adiagrammatic representation showing electric connection of the motor ofFIG. 58.

Referring to FIG. 58, the motor shown is similar to the motor of FIG. 13but includes a centrifugal switch generally denoted at 200 in place ofthe commutator 14 and the associated brushes of FIG. 13. Thus, thecentrifugal switch 200 is located between an iron core 214 and acommutator 210 on a rotary motor shaft 201.

Referring now to FIGS. 59 and 60, the centrifugal switch 200 includes acentrifugal switch body 208 which is secured to the rotary motor shaft201 and accordingly is rotated together with a rotor of the motor. Anannular permanent magnet 202 is located around the center of thecentrifugal switch 200.

The centrifugal switch 200 includes three centrifugal switch contacts203 each secured to the switch body 208 by means of a fastening screw203a and connected to a commutator element 210a, 210b or 210c asindicated at a point C in FIG. 61. Another switch contact 206 is securedsimilarly to the switch body 208 by means of a fastening screw 206a andconnected to a terminal as indicated at a point a in FIG. 61. A furtherswitch contact 207 is secured similar to the switch body 208 by means ofa fastening screw 207a and connected to a terminal as indicated at apoint b in FIG. 61.

The centrifugal switch contact 203 has at an end thereof a contactmember 205 for contacting with the switch contact 206 or 207 toselectively connect the terminal (a, b of FIG. 61) to the commutator210. The switch contact 203 further has a weight member 204 forcentrifugally moving the switch contact 203 effectively in a radiallyoutward direction. The weight member 204 has a property of beingattracted by the annular permanent magnet 202 and may nautrally be apermanent magnet itself. Thus, the centrifugal switch contact 203 hasthe contact member 205 thereon normally pressed against the switchcontact 206 by a spring force between the weight member 204 and theannular permanent magnet 202.

Now, operation of the centrifugal switch will be described.

While the rotational frequency and hence the rotational speed of thecentrifugal switch body 208 are sufficiently low, the centrifugal forceacting on the weight member 204 is smaller than the sum total of thespring force of the centrifugal switch contact 203 and the attractingforce acting between the annular permanent magnet 202 and the weightmember 204 so that the contact member 205 is contacted with andelectrically connected to the switch contact 206 as seen in FIG. 59. Inthis instance, the terminal a of FIG. 61 is connected to the commutatorterminal c so that electric current flows from a brush 212 through thecommutator element 210a, a coil L₂, another coil L₁, and the commutator210b to another brush 213.

Meanwhile, if the rotational speed of the centrifugal switch body 208rises until the centrifugal force acting on the weight member 204becomes greater than a resultant force of the spring force of thecentrifugal switch contact 203 and the attracting force acting betweenthe annular permanent magnet 202 and the weight member 204, then thecontact member 205 of the centrifugal switch contact 203 is moved out ofcontact with the contact member 206. At this instant, the commutatorterminal c is at a neutral position from both of the terminal a and theterminal b as seen from FIG. 61 so that electric current does not flowthrough the coils L₁ and L₂. Consequently, the rotational speed of themotor tends to drop. However, since the weight member 204 is spaced awayfrom the annular permanent magnet 202, the attracting force actingtherebetween now is very small while the centrifugal force acting on theweight member 204 is great comparing with the spring force of thecentrifugal switch contact 203. Consequently, the contact member 205 nowbecomes contacted with and electrically connected to the switch contact207 (refer to FIG. 59). In this instance, the commutator terminal c ofFIG. 61 is connected to the terminal b so that electric current flowsfrom the brush 212 through the commutator element 210a and then onlythrough the coil L₁ and through the commutator element 201b to the brush213. As a result, the motor is further accelerated until a predeterminedhigh speed is reached, and accordingly the contact member 205 of thecentrifugal switch contact 203 will not be brought out of contact withthe switch contact 207.

If the rotational speed of the motor drops due to increase of a loadapplied to the motor or by some other reason until the spring force ofthe centrifugal switch contact 203 becomes relatively greater than thecentrifugal force acting on the switch member 204, the contact member205 will be moved away from the switch contact 207. At this instant, noelectric current flows through the coils L₁, L₂, which will further dropthe rotational speed of the motor. Finally, the annular permanent magnet202 and the weight member 204 are contacted with each other, restoringthe initial condition as seen in FIG. 59. Consequently, electric currentflows again through the coils L₁, L₂ to drive the motor.

A driving circuit where the centrifugal switch described above isemployed may be a well known motor driving circuit of the bridge typesuch as, for example, a modification to the motor driving circuit ofFIG. 31 wherein the transistors Tr₈ and Tr₉ are omitted.

FIGS. 62 to 67 show a fifth embodiment of motor controlling system ofthe present invention. In the present embodiment, a modified centrifugalswitch is incorporated in a motor to which the motor controlling systemof the invention is applied, and in FIGS. 62 and 67, like parts orcomponents are denoted by like reference symbols to those of FIGS. 58 to61. Referring to FIGS. 62 to 67, a centrifugal switch body 208 issecured to a rotary shaft 201 of a motor and accordingly is rotatedtogether with a rotor of the motor. An annular permanent magnet 202 islocated around the center of the centrifugal switch 200.

The centrifugal switch includes a centrifugal switch contact 203 securedto the switch body 208 by means of a fastening screw 203a and connectedto a ring-shaped pattern 250a on a rotary disk 250 as shown in FIGS. 62and 65. Another switch contact 207 is secured similarly to the switchbody 208 by means of a fastening screw 207a and connected to anotherring-shaped pattern 250b on the rotary disk 250.

The centrifugal switch contact 203 has at an end thereof a contactmember 205 for contacting with the switch contact 207. The switchcontact 203 further has a weight member 204 for centrifugally moving theswitch contact 203 effectively in a radially outward direction. Theweight member 204 has a property of being attracted by the annularpermanent magnet 202 and may naturally be a permanent magnet itself.Thus, the centrifugal switch contact 203 has the contact member 205thereon normally spaced away from the switch contact 207 by a springforce of the switch contact 203 itself and an attracting force betweenthe weight member 204 and the annular permanent magnet 202. A pair ofsliding contacts 252a, 252b are secured at one ends thereof to a bottomwall 254 of the motor and are slidably contacted at the opposite endsthereof with the ring-shaped patterns 250a, 250b on the rotary disk 250,respectively.

While the rotational frequency and hence the rotational speed of thecentrifugal switch body 208 are sufficiently low, the centrifugal forceacting on the weight member 204 is smaller than the sum total of thespring force of the centrifugal switch contact 203 and the attractingforce acting between the annular permanent magnet 202 and the weightmember 204 so that the contact member 205 is spaced away from thecontact 207 as seen in FIG. 63. In this instance, the ring-shapedpatterns 250a, 250b are not electrically connected to each other.

Meanwhile, if the rotational speed of the centrifugal switch body 208rises until the centrifugal force acting on the weight member 204becomes greater than a resultant force of the spring force of thecentrifugal switch contact 203 and the attracting force acting betweenthe annular permanent magnet 202 and the weight member 204, then thecontact member 205 of the centrifugal switch contact 203 is contactedwith an electrically connected to the switch contact 207 (refer to FIG.64). Consequently, the righ-shaped patterns 250a and 250b areelectrically connected to each other and accordingly the slidingcontacts 252a and 252b are electrically connected to each other.

The sliding contacts 252a, 252b are connected to leads 255a, 255b,respectively, so that electric connection and disconnection thereof maybe transmitted to a circuit outside the motor.

If the rotational speed of the motor drops due to increase a loadapplied to the motor or by some other reason until the spring force ofthe centrifugal switch contact 203 becomes relatively greater than thecentrifugal force acting on the weight member 204, the contact member205 will be moved away from the switch contact 207.

Construction of a motor driving circuit wherein the centrifugal switchof FIGS. 62 to 65 is employed is shown in FIG. 66, and operation of themotor driving circuit is illustrated in a flow chart of FIG. 67. It isto be noted that the circuit of FIG. 66 is a modification to the circuitof FIG. 23 while the flow chart of FIG. 67 is a modification to the flowchart of FIG. 41. Accordingly, description of like components and likesteps of operation which are denoted by like reference numerals orsymbols will be omitted herein to avoid redundancy.

Referring to FIG. 66, it can be seen that an additional switch S₉ isprovided. This switch S₉ corresponds to a switch including the switchcontacts 205, 207 described above.

Referring now to FIG. 67, it can be seen that the steps #502 to #516 ofthe routine of FIG. 41 are replaced by a significantly reduced number ofsteps. In particular, in case the auto flag AUTOF indicating that thevoltage of the power source is higher than a predetermined voltage levelat which change-over of the speed of the motor is allowed is in the setstate at step #502, the motor is controlled at step #503 to rotate in alow speed high torque condition in the forward direction whereafter themicrocomputer μC waits at step #504' until the centrifugal switch S₉ isturned on. Then, when the centrifugal switch S₉ is turned on, the motoris changed over at step #506' to rotate in a high speed low torquecondition in the forward rotation. Thus, if winding of a film iscompleted during the high speed low torque forward rotation of themotor, which is determined at step #516' within a loop including thesteps #506', #508' and #516', then the motor is stopped at step #514. Onthe other hand, if the load applied to the motor increases during thehigh speed low torque forward rotation of the motor so that therotational speed is reduced until the centrifugal switch S₉ is turnedoff, which is determined at step #508' within the loop, then the motoris controlled at step #512 to rotate at a low speed in the forwarddirection again in order to complete the intended winding of the film.

In this manner, where a centrifugal switch such as the centrifugalswitch 200 of the embodiments of FIGS. 58 to 61 and FIGS. 62 to 67 isincorporated in a dc motor, the number of steps of operation in aroutine of a microcomputer can be reduced significantly.

As apparent from the foregoing description, according to the presentinvention, a dc motor can be changed over between a high speed lowtorque rotational condition and a low speed high torque rotationalcondition by change-over of electrical connection thereof. Accordingly,a driving force of the motor can be utilized effectively with a simpleand compact mechanical construction of the motor. Besides, according toa motor controlling system of the present invention, the drivingcondition of the dc motor can be changed over in response to a givencondition of the motor. Accordingly, the motor can be driven with highefficiency.

What is claimed is:
 1. A motor-controlling system for a dc motor,comprising:a dc motor having at least two coils; driving means fordriving said dc motor; first change-over means for changing connectionof said at least two coils to change over said motor, when power isselectively supplied to said at least two coils of said motor, from afirst driving mode in which the torque produced is relatively high andthe rotational frequency is relatively low to a second driving move inwhich the torque is relatively low and the rotational frequency isrelatively high; first selecting means for automatically selecting oneof the first and second driving modes within a consecutive movement ofsaid dc motor to control said first change-over means in response to agiven condition of said motor; second change-over means for allowingchange-over between a first controlling mode in which said firstselecting means is enabled and a second controlling mode in which saidfirst selecting means is disabled and said motor can be driven only inthe first driving mode in said consecutive movement; and secondselecting means for selecting one of the first and second controllingmodes to control said second change-over means.
 2. A motor controllingsystem according to claim 1, wherein said second selecting meansincludes a change-over operating switch and selects one of the first andsecond controlling modes in response to a condition provided by saidchange-over operating switch.
 3. A motor-controlling system according toclaim 1, wherein said second selecting means automatically selects oneof the first and second modes in response to a given condition of saidmotor in said consecutive sequence of movement.
 4. A motor controllingsystem according to claim 3, wherein said second selecting meansincludes detecting means for detecting a voltage of a battery andselects the first controlling mode when a voltage of said batterydetected before driving of said motor is started is higher than apredetermined level but selects the second controlling mode when such adetected voltage is not higher than the predetermined level.
 5. A motorcontrolling system for a dc motor, comprising:a dc motor having at leastfirst and second serially connected coils; driving means for drivingsaid dc motor; change-over means for changing over said motor between afirst driving mode in which one of the first and second coils is usedfor energization and a second driving mode in which the first and secondserially connected coils are used for energization; and motor stoppingmeans operable upon stopping of said motor for shorting said first andsecond serially connected coils irrespective of whether said motor isdriven in the first driving mode or in the second driving mode.
 6. Amotor controlling system according to claim 5, wherein said motorstopping means shorts opposite ends of the two serially connected coils.7. A motor controlling system according to claim 5, wherein said motorstopping means normally shorts opposite ends of each of said first andsecond coils.
 8. A motor-controlling system for a dc motor, comprising:adc motor having at least two coils; power supply means for supplyingelectric power to said dc motor; centrifugal force detecting meanshaving a switching means which is normally turned off by a spring forceand is turned on against the spring force by a centrifugal forceproduced by a rotation of said dc motor; and change-over means forchanging over the electrical connecting condition of said at least twocoils whereby, in response to the operation of said switching means, theoperation of changing over said motor between a first mode in which thetorque produced is relatively high and the rotational frequency isrelatively low and a second mode in which the torque is relatively lowand the rotational frequency is relatively high.
 9. A motor controllingsystem according to claim 8, wherein said dc motor has first and secondserially connected coils, and when the centrifugal force is greater thana predetermined level, said switch means turns on thereby to put saidmotor into the second mode in which electric power is supplied to onlyone of said first and second coils, but otherwise when the centrifugalforce is not greater than the predetermined level, said switch meansturns off thereby to put said motor into the first mode in whichelectric power is supplied to both of said first and second seriallyconnected coils.
 10. A motor-controlling system for use in a camera,comprising:a dc motor for operating the camera and having at least firstand second coils; power supply means for supplying electric power from abattery to said dc motor; change-over means for changing connection ofsaid at least first and second coils to change over said motor, whenpower is selectively supplied to said at least first and second coils,between a first mode in which the torque produced is relatively high andthe rotational frequency is relatively low and a second mode in whichthe torque produced is relatively low and the rotational frequency isrelatively high, and said change-over means serially connects said firstand second coils for simultaneous energization when said motor is in thefirst mode but connects either one of said first and second coils tosaid power supply means when said motor is in the second mode forselective energization of said first or second coil; means for examininga voltage of said battery; and selecting means for automaticallyselecting one of the first and second modes to control said change-overmeans in response to the voltage of said battery.
 11. Amotor-controlling system for use in a camera, comprising:a dc motorhaving at least two coils for producing power to drive a mechanism inthe camera; driving means for driving said dc motor; first change-overmeans for changing connection of said at least two coils to change oversaid motor, when power is selectively supplied to said at least twocoils of said motor, between a first driving mode in which the torqueproduced is relatively high and the rotational frequency is relativelylow and a second driving mode in which the torque is relatively low andthe rotational frequency is relatively high; first selecting means forautomatically selecting one of the first and second driving modes withina consecutive movement of said dc motor to control said firstchange-over means in response to a given condition of said motor; secondchange-over means for allowing change-over between a first controllingmode in which said first selecting means is enabled and a secondcontrolling mode in which said first selecting means is disabled andsaid motor can be driven only in the first driving mode in saidconsecutive movement; and second selecting means for selecting one ofthe first and second controlling modes to control said secondchange-over means.
 12. A motor-controlling system for a dc motor,comprising:a dc motor having at least two coils; power supply means forsupplying electric power to said motor; change-over means for changingconnection of said at least two coils to change over said motor, whenpower is selectively supplied to said at least two coils of said motor,between a first mode in which the torque produced is relatively high andthe rotational frequency is relatively low, and a second mode in whichthe torque is relatively low and the rotational frequency is relativelyhigh; and selecting means for automatically selecting one of the firstand second modes within a consecutive movement of said dc motor tocontrol said change-over means wherein said selecting means selects thefirst mode when said dc motor is started to rotate and selects thesecond mode when a voltage of said battery returns to a predeterminedlevel after it drops when the dc motor is started to rotate.
 13. Amotor-controlling system for a dc motor as set forth in claim 12,wherein said dc motor operates a film winding and rewinding device in acamera.
 14. A motor-controlling system for a dc motor as set forth inclaim 12, wherein said motor includes first and second coils, and saidchange-over means connects said first and second coils in a serialrelationship for simultaneous energization when said motor is in thefirst mode but connects either one of said first and second coils tosaid power supply means when said motor is in the second mode forselective energization of said first or second coil.
 15. Amotor-controlling system for a dc motor, comprising:a dc motor having atleast first and second coils; power supply means for supplying electricpower to said motor; change-over means for changing connection of saidat least first and second coils to change over said motor, when power isselectively supplied to said at least first and second coils of saidmotor, between a first mode in which the torque produced is relativelyhigh and the rotational frequency is relatively low, and a second modein which the torque is relatively low and the rotational frequency isrelatively high, and said change-over means serially connects said firstand second coils for simultaneous energization when said motor is in thefirst mode but connects either one of said first and second coils tosaid power supply means when said motor is in the second mode forselective energization of said first or second coil; and selecting meansfor automatically selecting one of the first and second modes within aconsecutive movement of said dc motor to control said change-over meanswherein said selecting means selects the first mode when said dc motoris started to rotate and selects the second mode when the rotationalfrequency of said dc motor rises a predetermined level.
 16. Amotor-controlling system for a dc motor, comprising:a dc motor having atleast first and second coils; controlling means for controlling anoperation of said dc motor at one of a first mode in which the torqueproduced is relatively high and the rotational frequency is relativelylow, and a second mode in which the torque is relatively low and therotational frequency is relatively high; and change-over means forchanging over said controlling means between the first and second modesin response to a variation of a rotational frequency of said dc motor,and said change-over means serially connects said first and second coilsfor simultaneous energization when said motor is in the first mode butconnects either one of said first and second coils to said power supplymeans when said motor is in the second mode for selective energizationof said first or second coil.
 17. A motor-controlling system for a dcmotor as set forth in claim 16, wherein said dc motor operates a filmwinding and rewinding device in a camera.
 18. A motor-controlling systemfor a dc motor, comprising:a dc motor having at least first and secondcoils; power supply means for supplying electric power to said motor;change-over means for changing connection of said at least first andsecond coils to change over said motor, when power is selectivelysupplied to said at least first and second coils of said motor, betweena first mode in which the torque produced is relatively high and therotational frequency is relatively low, and a second mode in which thetorque is relatively low and the rotational frequency is relativelyhigh, and said change-over means serially connects said first and secondcoils for simultaneous energization when said motor is in the first modebut connects either one of said first and second coils to said powersupply means when said motor is in the second mode for selectiveenergization of said first or second coil; and selecting means forautomatically selecting one of the first and second modes within aconsecutive movement of said dc motor to control said change-over meanswherein said selecting means selects the first mode when said dc motoris started to rotate and selects the second mode when a predeterminedtime elapses after the dc motor is started to rotate.